For most of San Francisco’s history, its heart and soul was its port.

The City Front, as the waterfront was called, was the engine that drove the city’s economy. Every day, it swarmed with longshoremen, sailors and other workers of all sorts, as well as thousands of people coming and going from the trains, buses, cable cars and taxis that connected with the Ferry Building.

In 1933, in the depths of the Depression, 7,000 ships entered and left the city’s 82 piers. Most of those ships carried cargo that had to be loaded or discharged — longshoremen’s work.

It was hard, dangerous labor. The bars and cafes on East Street, as the Embarcadero was called, were no strangers to men on crutches, missing fingers or eyes, or otherwise scarred by years of toil grappling with heavy loads on the piers, in the holds and on the decks. San Francisco, or at least the City Front, was truly Muscle City.

The vast majority of goods handled at San Francisco was so-called break-bulk cargo. This was cargo that could be broken into pieces — barrels, boxes or sacks — capable of being handled by one man or a small team.

It was not a job for a 98-pound weakling. A 1932 U.S. Bureau of Labor Statistics bulletin by Boris Stern, titled “Cargo Handling and Longshore Labor Conditions,” describes some of the cargo that men or teams of men were expected to lift. They ranged from bags of flour (100-150 pounds) to coffee (135-200 pounds) to linseed and other oils (200-300 pounds) to bales of Egyptian cotton (750 pounds) to hogsheads of tobacco (500-1,000 pounds).

Obviously, a single longshoreman was not expected to lift a 1,000-pound hogshead of tobacco. But he was expected to handle a 330-pound bag of raw Cuban sugar. To place this in context, it’s worth noting that federal regulations now specify that one person is not to lift more than 50 pounds.

As Stern writes, the “essential requirements for the job of a longshoreman are a mighty arm, a hard muscle, and a large, strong back.” He also notes that learning how to load a ship in such a way as to make the best use of the space without the cargo shifting, which could damage it or the vessel, took several years to learn.

Such work, he writes, “is undoubtedly skilled labor, and should be classified as such.”

The port’s modern heyday came during the late 1930s, when San Francisco was the second-largest port in the U.S. in the value of its cargo. Different parts of the port specialized in different cargo. Copra — dried coconut meat used to make coconut oil — was processed at the “copra dock” at Pier 84, on Islais Creek. Bananas were stored at Pier 60, on the south side of Channel Street. Pears, apples, plums and grapes from the Central Valley were stored at a State Shipside Refrigeration terminal on the north side of China Basin. Vegetable oils were loaded at Pier 38, at the foot of Townsend Street.

As Michael Corbett notes in “Port City: The History and Transformation of the Port of San Francisco, 1848-2010,” improvements in the moving of cargo took place over decades, often in incremental steps.

In the port’s early days, cargo was moved by man- or animal-powered winches connected to booms. In 1881, the steam donkey, a portable steam engine, replaced human and animal power. In 1920, the port began supplying electrical power to the piers.

The Bureau of Labor’s 1932 bulletin details how various types of cargo were moved in San Francisco in the 1920s and ’30s. Most of the gear used — powered winches, cables and booms — was aboard the ships, not on the piers.

The simplest means of loading cargo, the “whip,” involved one winch and one boom. The boom was placed over the cargo hatch. Longshoremen would load cargo onto a sling on the apron of the pier. The “fall” — the cable — was passed around the winch and connected to a hook that held the sling.

The winch was started and the sling was dragged up a ramp, or skid, over the railing of the ship and above the hatch. The sling was then lowered into the hatch. The sling was prevented from swinging side to side by a worker holding a rope attached to the hook.

Workers in the hold would unload the cargo, the sling would be winched out, and the process would begin again. For unloading cargo, the whip was insufficient and two booms and two winches were used.

The work was performed by groups of longshoremen known as gangs, which varied from 12 to 40 men. The speed with which gangs could move cargo was crucial to the economic success of the shipping line, and the amount of break-bulk cargo longshoremen could move, using relatively primitive methods, is remarkable.

San Francisco, for example, was unmatched at loading raw sugar, which arrived from Hawaii in bags weighing 135 pounds. In 1926, San Francisco longshoremen recorded an average of 1,681 bags per gang-hour, a rate equaled only by New York.

The arrival of container ships in 1958 spelled doom for San Francisco as a working port. As a child in the 1960s, I watched longshoremen using a boom and a sling unloading bales of cargo at a pier north of the Ferry Building. But that was break-bulk’s last hurrah.

The great piers where sweating men hauled heavy loads onto and off ships from around the world now house cruise ships or design firms, or stand empty. The Port of San Francisco still handles some cargo. But Muscle City is gone forever.

Gary Kamiya is the author of the best-selling book “Cool Gray City of Love: 49 Views of San Francisco,” awarded the Northern California Book Award in creative nonfiction. All the material in Portals of the Past is original for The San Francisco Chronicle. To read earlier Portals of the Past, go to sfchronicle.com/portals. For more features from 150 years of The Chronicle’s archives, go to sfchronicle.com/vault. Email: metro@sfchronicle.com

Trivia time The previous question: Nob Hill had two earlier names. What were they? Answer: Fern Hill and the Clay Street Hill. This week’s trivia question: Which San Francisco journalist’s body lay in state in City Hall in 1936? Editor’s note Every corner in San Francisco has an astonishing story to tell. Gary Kamiya’s Portals of the Past tells those lost stories, using a specific location to illuminate San Francisco’s extraordinary history — from the days when giant mammoths wandered through what is now North Beach to the Gold Rush delirium, the dot-com madness and beyond. His column appears every other Saturday, alternating with Peter Hartlaub’s OurSF. Dig deep into Chronicle Vault Like what you’re reading? Subscribe to the Chronicle Vault newsletter and get classic archive stories in your inbox twice a week. Read hundreds of historical stories, see thousands of archive photos and sort through 153 years of classic Chronicle front pages at SFChronicle.com/vault.