In the annals of rum history, Puerto Rico often gets short shrift. While the stories of Barbados, Jamaica, and Martinique rums are well trod ground for writers, Puerto Rico’s rum story is far less known despite being today’s largest producer of Caribbean rum.

One reason for the lack of attention among enthusiasts is that the countless millions of gallons of light “silver” rums flowing from Puerto Rico don’t stoke the passions of rum connoisseurs. The island is much more than these light rums however.



Another reason Puerto Rico’s story isn’t told as often is that it’s only been a significant exporter of rum for eighty years. But look past these reasons and you’ll see a rich history with plenty to excite rum lovers. When it comes to Puerto Rican rum, only one producer has been there since the beginning: Destilería Serrallés.

I recently visited their distillery and came away with a far deeper appreciation for their central role in Puerto Rican rum history. And what they’re doing today is equally impressive. Before jumping into the modern-day details of Destilería Serrallés, let’s hop in the time machine, set the dial for the early 1800s, and see how it came to be.

A Brief History of Serrallés and Puerto Rican Rum

Our story begins in the 1820s when Sebastián Serrallés arrives in the Spanish colony of Puerto Rico. At this point in history, Caribbean sugar cane production had been going strong for nearly two centuries. Sebastián soon established a sugar cane estate in Ponce on the southern coast of the island, where Destilería Serrallés is still based today.

It was Don Juan Serrallés, Sebastián’s son, who led the family into the rum business in 1865 by purchasing a small French-made batch still topped with a short neck with several plates. Also around this time, Facundo Bacardi began distilling in another Spanish colony: Cuba. It was the start of many rum-related happenings connecting the two islands.

Around 1890, both Cuba and Puerto Rico acquired their first column stills, setting the foundation for the “Spanish heritage” style of rum, characterized by a relatively short molasses ferment, column distillation, blending of light and heavier rums, and a lighter flavor profile when compared to pot still rums from Jamaica, Guyana and elsewhere. By 1897, there were 198 distilleries on Puerto Rico producing over 1.6 million gallons of rum, most which was consumed locally. Compared to other Caribbean colonies, this was a relatively moderate amount at the time.

1898 brought the Spanish-American war, a relatively quick conflict ending decisively in America’s favor and starting it on the path to world power status. The 1898 Treaty of Paris effectively gave the U.S. control over Puerto Rico and Cuba, along with other Spanish territories including Guam and the Philippines. However, while Cuba gained formal independence in 1902, Puerto Rico remains a U.S. territory to this day.

Spanish-American War depiction

In 1917, the U.S. Congress enacted the rum cover-over provision. In brief, federal taxes collected from Puerto Rican manufacturers were sent back, or covered-over, to the Puerto Rican treasury. This includes the excise tax on distilled spirits. The goal of the cover-over was to supply funds to the local government for infrastructure improvements and related causes. The details of the rum cover-over are enormously complicated and addressed elsewhere, so I will leave it at that for now. However, it should be noted that the rum cover-over exists to this day, both for Puerto Rico and for the U.S. Virgin Islands.

1917 also brought prohibition to Puerto Rico, two years prior to the States. However, a small amount of “medicinal” rum production was sanctioned, similar to medicinal whiskey production in Kentucky during prohibition. Several rum makers on the island, including Serrallés, remained in business by temporarily switching to other types of production.

The end of prohibition in 1933 lit the big bang moment for Puerto Rican rum. Distilleries started making rum again with gusto, eager to supply the now-legal U.S. market. Serrallés was quick out of the gate to capitalize on the opportunity. They expanded production capacity by adding a five-column still which allowed them to make either rum or fuel ethanol; whichever was most in the demand at the moment.

Prohibition’s end also brought a new tax scheme on spirits imported into the U.S.; the upshot was that domestically made spirits paid less taxes. So big was the American market that Bacardi, then operating primarily in Cuba, saw financial benefit in building a new distillery in Puerto Rico in 1936 to provide rums for the American market.

As the 1930s segued into the 1940s rum production in Puerto Rico grew substantially every year. With increased production came increased excise taxes feeding the island’s treasury by way of the cover-over. During this time, vast amounts of public works were effectively subsidized by Puerto Rican rum sales.

The onset of the U.S. entering World War II in late 1941 lit the afterburners of Puerto Rico’s rum economy. U.S. wartime regulations required reserving grain for war-related purposes, effectively shutting down American whiskey production. Rum from Puerto Rico and elsewhere in the Caribbean flooded into the U.S. to fill the gap left by the whiskey industry pause.

To give a sense how much rum production rose during the WW II era, in 1940 Puerto Rico shipped 1.4 million gallons to the U.S. Four years later in 1944, it was six million gallons. In that year, the island made 7.3 million gallons of rum, but sources indicate it was capable of making at least 14 million gallons.[1]

With every boom comes a bust. For Puerto Rico’s rum makers, it was the end of World War II when mainland whiskey distilleries resumed production. Furthering Puerto Rico’s woes, the ravenous wartime call for spirits of any kind had the island shipping unaged or very lightly aged rum as soon as it was made. Relatively little or no high-quality aged stocks remained in warehouses.

With the island so dependent on cover-over money from the rum industry, the government worked quickly to restore rum-related revenues. One approach was improving the reputation of the island’s rum by setting a minimum quality bar on exported rum.

Those regulations still exist today. In brief, genuine Puerto Rican rum must be:

Distilled and aged in Puerto Rico

Molasses based

Distilled in a continuous column

Aged for a minimum of 1 year in American white oak barrels

Another blow to Puerto Rico’s rum industry in the post-war era was the demise of the island’s sugar cane industry. The once plentiful molasses that distilleries relied on began to come from elsewhere. A sad reminder of Puerto Rico’s once great sugar industry is just across the road from Destilería Serrallés: The long-shuttered remains of the Serrallés sugar factory.

Defunct Serrallés sugar factory

The 1959 Cuban Revolution left Bacardi without their Cuban facilities so Puerto Rico became the new center of their distilling operations. Over the following decades grew to become the largest Caribbean rum brand and a household name around the world.



Meanwhile, the Serrallés family business also expanded rapidly and in 1985 they acquired the assets of Puerto Rico Distillers, Inc., a subsidiary of the Canadian spirits giant Seagram’s. The acquisition brought additional brands such as Ronrico and Palo Viejo to the Serrallés portfolio.



That deal also gave Serrallés the rights to produce and distribute Captain Morgan rum in the Caribbean; they made an enormous quantity of it over the following decades. In 2007, partially in anticipation of more Captain Morgan business, Serrallés substantially increased their distillation capacity by adding a second multi-column still to replace most of the original 1934 still. (The “beer” column is still used today. More on that later.)

In 2011, Diageo, who by then had purchased the Captain Morgan brand, opted to discontinue its license with Serrallés and move production to St. Croix USVI. This move was in part due to Diageo striking a favorable financial deal with the USVI government involving parts of the cover-over money.

In 2019, Serrallés announced a major $22 million expansion, including increased distillation capacity and upgrades to their bottling line capacity.

The Don Q Brand

In 1934 Serrallés inaugurated the Don Q brand. Don Q refers to Don Quixote, the main character from the eponymous novel by Miguel de Cervantes. The brand has been continuously sold in the U.S. since then, albeit waxing and waning in availability. The Don Q brand is Serrallés’ premium export brand, as well as the number one selling rum in Puerto Rico.

Boca Chica and Don Q are both longstanding Serrallés brands.

Besides Don Q, the company also makes cane-based vodka, as well as other local rum brands such as Palo Viejo, which is the number two selling rum brand on the island.

In the early years, Don Q was imported into the states via national importers like Schieffelin and Heublein. Seeking to better control things, Serrallés set up Don Q Imports in the 1960s to manage their own importing. By the 1980s Don Q Imports was shuttered, although the brand remained in a few states via an agency arrangement with Jim Beam. In 2006, Serrallés USA was formed to essentially re-launch the brand and broaden its distribution within the U.S.

Conveniently, this brings us to the topic of Roberto Serrallés, once the president of Serrallés USA and current Vice President of Business development .

Roberto Serrallés (right) outside of Serrallés administration building. Sugar factory in distance.

Roberto Serrallés – 6th Generation of Rum Making

Destilería Serrallés is one of the few remaining family-owned Caribbean distilleries. Although the current CEO, Philippe Brechot, is not a family member, the rum making tradition lives on with Roberto Serrallés. Roberto is on the company’s board of directors, as well as Vice President of Business development and an architect of the Serralles USA venture. Roberto is no bean counter. He’s very hands on, taking a substantial role in modernizing operations and substantially reducing environmental impact – more on this later.



Now in his early 50s, Roberto is very personable and passionate. After growing up in Puerto Rico, he headed to the U.S. mainland where he obtained his PhD in environmental studies from the University of Oregon. Originally thinking he would remain in academia, he was instead brought back into the family business in 2004 to help with wastewater treatment issues. His role has increased substantially since then and he frequently represents the company at rum events around the world.

Roberto Serrallés

As a former academic, it’s not surprising that Roberto is very enthusiastic about teaching. During our visit Roberto brought us into his office, sat us in front of a whiteboard, and spent 45 minutes animatedly described rum making at Serrallés in astonishing detail; You might even think he was born with a whiteboard marker in hand!

Spanish Heritage Rum, Bases, and Blending

Before geeking out over the Serrallés distillery details, it’s helpful to understand the type of rum that Serrallés makes. Many rum producers from former Spanish colonies such Cuba, Puerto Rico and Panama make rum in a common style that some call “Spanish Style,” although I prefer “Spanish Heritage”.

The common threads that connects Spanish heritage rums include most or all of the following:

A molasses wash and a relatively short fermentation of a day or two.

Use of cultured yeast rather than wild yeast fermentation

Column distillation

Distilling both light rum (around in 94 percent ABV) in several columns, and heavier rum (around 75 percent ABV) in a single column

Blending light and heavy column rum together to make a variety of rum “bases” to complement the light and heavy rums.

Aging three or more base rums (light, medium, heavy) separately, then blending them together prior to bottling.

Serrallés follows this basic model of rum making, as does Bacardi, Havana Club, Angostura, and numerous other distilleries. To read more about this, see my Cuban Rum Cheat Sheet.

It’s important to note that there are some distilleries from Spanish heritage countries like Venezuela that incorporate batch stills and other techniques into their rum making. These rums are outside of the particular Spanish heritage definition I gave above.

Into the Distillery

Let’s put on our hard hats and join Roberto in his golf cart to enter the heart of Destilería Serrallés, travelling through it in the same sequence that rum production follows.

Destilería Serrallés is traversed by golf carts

The distillery is located in Ponce, about 3.5 miles from Puerto Rico’s southern coast, roughly equidistant from the east and west coasts. Several rivers flow through the mountains rising in the distance to the north. One of these rivers has a historical connection to the distillery.

Water

Water is the lifeblood of distilling. A distillery without a reliable, high quality water source won’t stay in business for long. I start every distillery tour by asking about its water source.

Destilería Serrallés has a great story in this regard. The Río Inabón river winds through Puerto Rico’s volcanic mountains and is one of fourteen rivers in the Ponce region. Per the company’s site, the 1898 Treaty of Paris granted exclusive use of the Río Inabón to the Serrallés family business.

Molasses

As our golf cart approaches the main distillery building, I spy several enormous molasses tanks of varying sizes. According to Roberto, imported molasses is approximately seventy percent of the direct cost of making rum here. If sugar cane and the resulting molasses were available locally, that figure could be substantially less. Unfortunately, a recent Serrallés experiment to grow sugar cane and possibly reintroduce it on a wider scale was wiped out by Hurricane Maria in 2017.

Molasses storage

With no local molasses source, the distillery imports it from the Dominican Republic, Guatemala, and sometimes other sources. Getting high quality molasses with sufficient sugar content to ferment successfully is challenging. With increasingly efficient sugar cane processing, fewer fermentable sugars remain in the molasses. Dominican Republic molasses is usually the lowest cost but must be blended with “high test” molasses to increase the sugar levels. High test molasses is just partially inverted cane syrup from which no sugar has been removed.

The distillery keeps around 9 million gallons of molasses on site. At the nearby port you’ll find another 2 million gallons in reserve.

Fermentation

At Serrallés, fermentation starts by diluting the molasses blend with water down to 40 brix. (Brix is the amount of sugar in a water solution.) The molasses/water mix blend is then heated and kept at 170 Fahrenheit for five minutes to pasteurize it. Afterwards, it’s is further reduced with more water to 20 brix, ready for fermentation.

Molasses pasteurization isn’t particularly common in the rum world. It eliminates any wild yeast and bacteria, thus enabling a more consistent product fermented only with the desired yeast strain. In contrast, pasteurizing would be anathema at a distillery like Hampden Estate or River Antoine which rely on natural, airborne yeast for their unique flavor.

The yeast Serrallés uses is a special strain, isolated in the 1950s. It goes into one of fourteen fermentation tanks that feed the nearby column stills. The nine original tanks hold 35,000 gallons each. They were later augmented by four more 70,000 gallons tanks. Two additional 200,000 gallons tanks round out the lot. As you would expect in an operation that values consistency, all fermenters are temperature controlled to prevent the fermenting liquid from getting too warm.

There are two primary fermentation protocols used at Serrallés; one for light rum, the other for heavy rum.

Approximately 95 percent of the rum made at Destilería Serrallés is light rum, made using a 40 to 44-hour fermentation, resulting in a wash of around nine percent ABV.

In contrast, heavy rum (the other five percent of the rum made there) uses a substantially longer seven to ten-day ferment and yielding a similar nine percent ABV wash.

Distillation

Our golf cart comes to a rest near a large factory-looking building, which in fact it is – a rum factory. Roughly six stories tall and partially sheathed in corrugated metal siding, it holds a menagerie of metal pipes, columns and walkways going every direction imaginable. Embedded somewhere within the maze is the 1934-built column still that made all the company’s rum till 2007.

Stillhouse containing 1934 column still

Portion of 1934 column still

Stepping inside, we come face-to-face with one of its very large and tall columns. It’s reminiscent of the many bourbon stills in Kentucky. The resemblance is further confirmed by the “VENDOME” on the many oval portal doors running up the still that allow access to the plates within. Stills made by Vendome Copper & Brass Works are synonymous with American bourbon, but here we find one in the Caribbean, thousands of miles from the Bourbon heartland.

1934 column still – Note: “VENDOME, LOUiSVILLE” on portal door.

The first column, aka the “beer” column has over a dozen plates within. It’s the only portion of the original five column still in everyday use. Operated at full capacity, the 1934 still could pump out 12 million proof gallons of rum per year. These days the beer column is used exclusively for distilling the Serrallés heavy rum which emerges at around 75 percent ABV.

Next, Roberto and his golf cart take us on a very short ride to a very different looking distilling apparatus. Unlike the confusing maze of equipment within the 1934 stillhouse, the 2007-built five-column still is easy to pick out from the surroundings. Encased within a neat grid of orthogonal beams and walkways, the silver columns jut into the sky.

2007 five-column still

Run at full capacity, the 2007 still is capable of 22 million proof gallons of rum per year. It distills the company’s light rum, which comes off at approximately 94.5 percent ABV. Our time was short, so we didn’t ascend the stairways to view the distillery from above. Instead, we made a quick stop at the distillery control center to gawk at the phalanx of monitors showing key distillery operations in real time.

Traditional Aging

Another spin in the golf cart takes us to one of several on-site aging warehouses. In total, the company has somewhere around 100,000 to 110,000 casks of rum in stock. The vast majority are ex-bourbon casks, but a few surprises await us. More on that in a bit.

Light rum enters the cask at between 55 to 65 percent ABV, while the less plentiful heavy rum goes is casked between 65 and 75 percent ABV. According to Roberto, around 5,000 casks reach the end of their useful life each year and are pulled from service. A little math shows that the typical cask spends about twenty years in service here.

Destilería Serrallés aging warehouse

Tapping some 18-year light rum for our group to blend with.

Pretty barrel pictures

But wait, there’s more! Like many distilleries, Serrallés consolidates casks of the same vintage rum. For example, ten casks that are each 70 percent full could be consolidated to just seven casks, each 100 percent full. Eliminating the air space in a cask reduces evaporation, aka the angel’s share. It also frees up casks to use with the next rum batch.

Earlier, I mentioned that besides light and heavy rum, Serrallés also makes three medium rum bases by blending light and heavy rums prior to aging. The three types are differentiated by the ratio of light and heavy rums in them. Although the numbers aren’t exact, Roberto says that the ratios are around 25/75, 50/50, and 75/25 percent.

Solera Aging

Entering the aging warehouse designated for visits like ours, it’s impossible to miss the rows of sherry casks, stacked vertically, three-high. In total, there’s 131 casks. Yes, what we have here is a solera, and a real one at that. Not one of those faux-soleras that rum enthusiasts rail against. These casks once aged Osborne Oloroso sherry, but now hold a small proportion of Serrallés’ rum for decades. A solera in Puerto Rico isn’t too surprising, given the island’s long history as a colony of Spain, where solera aging originated.

3-level solera at Destilería Serrallés

Technically, what Serrallés has is a three-level solera, meaning it has two criaderas (levels), with the bottom (oldest) level being the actual solera. Sherry soleras in Spain typically have many more levels, but a three-level solera is nothing to sneeze at. In order to keep things simple for those not versed in solera terminology, I’ll just call them the youngest, middle, and oldest levels.

Heavy rum with at least four years of ex-bourbon cask aging goes into the youngest level. Rum in the middle level has an average age of around 20 years and is occasionally replenished with rum from the youngest level. As for the oldest (bottommost) level, the rum within those casks is occasionally replenished with rum from the middle level. Within the oldest level there is rum up to 53 years old, i.e., when the solera started.

Solera aged rum (left), heavy rum (right)

You’re probably wondering how this solera aged rum tastes. During a “build your own blend” session with Roberto, we found out. It’s very, very intense, even for someone who drinks super high ester Jamaican rums and Grand Arôme without flinching. After many decades in a cask, the solera rum is extremely tannic, yet rich with other flavors. It’s assuredly a rum for blending in very small quantities with lighter rums, much like bitters in a cocktail.

Behind the enormous solera, we spied more large casks resting on the floor. A peek at their label revealed that some were ex-vermouth casks, some were ex-sherry casks, and a few I can’t reveal. These casks are the final step in creating the Don Q limited editions, which to date consist of the Vermouth Cask Finish and Sherry Cask finish rums.

More casks, including a Mancino Vermouth cask

Destilería Serrallés & Bulk Rum

Puerto Rico has two of the largest rum distilleries in the world. In terms of case volume, Bacardi is by far the largest Caribbean rum brand in the world, selling 17.1 million 9-liter cases in 2018. However, when it comes to bulk rum for export, Serrallés is the top dog on the island. According to experts, the distillery is among the largest bulk rum producers in the Caribbean.

At the time of this writing, the distillery is capable of producing 22 million proof gallons of rum per year, which isn’t to say it always makes that quantity. Of the rum made, approximately twenty percent goes to company owned brands like Don Q and Palo Viejo. The remaining 80 percent is exported as unaged bulk rum.

Some within the rum industry have portrayed bulk rum producers and their five column stills as incapable of making high quality rum. However, with the right equipment and expertise, a distillery can make both high quality rum as well as light, bulk rum. One does not prevent the other and it’s a common model for many Caribbean distilleries.



In today’s market, there’s a demand for bulk rum, and it doesn’t make economic sense for large distilleries to limit production to just what they age and sell themselves. There’s a lot of money tied up in human and physical capital, molasses storage, fermenters, control rooms and other items common to both types of rum making. To not capitalize on that is to leave money on the table.

Environmental Initiatives

Given Roberto’s passion for environment issues, it’s no surprise that the distillery is on the leading edge of reducing environmental impact. There are three main thrusts: Clean water, energy efficiency, and carbon dioxide emissions.

Yet more big tanks.

Clean Water

Distilleries use a phenomenal amount of water for fermentation, distillation, and other uses. Three times more wastewater is created than alcohol produced! The resulting wastewater has many compounds that can harm the environment in sufficient quantity. In the old days, this water might have been dumped into a field or drained into the ocean without extensive treatment. In the modern era, this isn’t acceptable.

Over time, Roberto developed a complex system to process wastewater. I won’t attempt to describe it in full detail here but will instead convey some key points. A graphical version of it can be found on the DonQ site if you want to learn more.

The system uses both aerobic and anaerobic digestions, which use bacteria to break down compounds into other forms and make them more easily separable from water. The methane gas that results from anerobic digestion can be collected for later use. The company has tested separating some of the solids from the wastewater through centrifuges and is evaluating mixing it with wood chips from shipping palettes to create an industrial compost. After the wastewater treatment, the resulting water is clean enough for irrigation.

Energy Efficiency

Distilleries also use a phenomenal amount of energy to heat water and pump things around. Destilería Serrallés previously consumed around two million gallons of crude oil per year towards that end. However, after collecting the methane generated during wastewater treatment, the distillery uses it as an alternative fuel source. Nowadays, the methane (with additional treatment), may supply about fifty percent of the distillery’s energy, saving around one million gallons of crude oil annually.

Another win on the energy front comes from a rather clever use of solar power. With storage for 100,000 casks, there’s plenty of roof area atop the aging warehouses, making a perfect spot for solar panels. The panels create one megawatt of power for use by the distillery. That’s nice, but not the clever part!

Solar panels on aging warehouse roof

The solar panels also shield the warehouse roof from direct sun, thus reducing the warehouse internal temperature. This reduction in temperature leads to lower evaporative losses from casks, i.e. the angel’s share. Measurements taken with and without the panels showed the angel’s share went down by one percent, e.g. from six percent to five percent annually. The amount of rum “saved” paid for the panels within six months!

Carbon Dioxide Emissions

All the fermenters at Serrallés are closed, rather than open air. Fermentation creates large amounts of carbon dioxide, which has a negative environmental impact in sufficient quantity. The company has collected it for use by the local island soda manufacturers for carbonating their beverages.

Unfortunately, the U.S. government recently changed regulations for the allowed refrigerants needed to condense the gas into liquid form. As such, the company is undergoing an expensive process to rework their equipment to be compliant and start collecting it again.

Besides making less expensive carbon dioxide for local companies, collecting it also reduces the amount of carbon dioxide shipped to the island from elsewhere, further reducing environmental impact.

While collecting carbon dioxide from fermentation isn’t unique to Serrallés, it’s still worth highlighting as an approach that distilleries take to go “greener”.

Expression Notes

Having seen firsthand the various base rums that Serrallés makes, I was finally able to wrap my head around exactly what’s in the many expressions they offer. These details come from Don Q Global Ambassador Alexx Mouzouris and Roberto. Some of them may surprise you!

Main Lineup

Don Q Cristal: A blend of light rums aged from 1.5 to three years. Charcoal filtered.

Don Q Gold: A blend of light rums aged from two to five years.

Don Q Añejo: A blend of light and medium rums aged from three to eight years.

Gran Añejo: A blend of light, medium and heavy rums aged nine to twelve years. Also contains some rum from the oldest solera level (up to 53 years.)

151: A blend of medium and heavy rums aged from 1-5 years.

Caliche: A blend of three, four, and five-year light and medium rums, plus a bit of medium level solera rum. Charcoal filtered. (Note: Caliche is not part of the Don Q lineup but is a lovely and flavorful lightly aged/filtered rum.)

Limited Editions

2005 Single Barrel: 100 percent light rum. Distilled in 2005. Casked at 65 percent ABV.

2007 Single Barrel: 100 percent medium rum. Distilled in 2007. Aged for nine years. Casked at 60 percent ABV.

2009 Single Barrel: 100 percent light rum. Distilled in 2009. Casked at 75 percent ABV in used Canadian whiskey casks (Two cycles of three years aging the whiskey). By Serrallés standards these were relatively young casks. The U.S. release is bottled at 40 percent ABV, while the European release is at 49.25 percent ABV.

Vermouth Cask Finish: A blend of light, medium and heavy rums. Aged for five to eight years. Finished for four to six weeks in Mancino Vermouth Vecchio casks. (Vecchio is a sweet, red vermouth.)

Sherry Cask Finish: A blend of light, medium and heavy rums. Aged for five to eight years. Finished for one year in an Osborne Oloroso sherry cask.

Gran Reserva de la Familia Serrallés: Medium rum. Aged for twenty years. Note: Only 1865 bottles were made. It celebrates the 150th anniversary of the Serrallés company making rum and is priced at $1865.

Having visited Destilería Serrallés, I have a new appreciation for the island’s historical place in rum making. While some people choose to mischaracterize the island’s rum as flavorless, the reality is far different. Puerto Rico now has plenty of great rums to excite the connoisseur’s palate, and a bright future ahead of it.



Chilling equipment

Still figuring out this safety helmet thing

Roberto humors The Wonk with a selfie by the solera

[1] Condition of Puerto Rican Sugar Industry: Hearings Before the Committee on Insular Affairs, House of Representatives, Seventy-ninth Congress, First Session, on Condition of Puerto Rican Sugar Industry, Washington, D. C; U.S. Government Printing Office, 1945