UNION -- A restoration project at Liberty Hall Museum's wine cellar unearthed spirits 221 years old that had been shipped to the sleepy Elizabethtown cottage shortly after the American Revolution.

During the six-month revamp, the museum discovered almost three cases of Madeira wine from 1796 and about 42 demijohns from the 1820s.

Some of the original Madeira stock was shipped to the second generation who lived at Liberty Hall, in anticipation of John Adams' presidency. Although Liberty Hall President John Kean was well aware of the wine collection, he couldn't have imagined its historical significance.

"We knew there was a lot of liquor down here, but we had no idea as to the age of it," said Kean, first cousin to New Jersey's former governor. "I think the most exciting part of it was to find liquor, or Madeira in this case, that goes back so far. And then trying to trace why it was here and who owned it."

Liberty Hall is located at Kean University, which was founded in 1855 and is one of New Jersey's largest state colleges. The 150-acre campus enrolls about 13,000 students each year, and is best known for its teaching program.

Whether it's telling the story of the Civil War or an esteemed visit by President William Howard Taft in 1909, the goal of the renovation is to walk visitors through every era of American history, said Bill Schroh Jr., director of operations at Liberty Hall.

"And Madeira was just one piece of that whole story," he said.

The project began in October 2015, and included an overhaul of the museum's wine cellar, rebuilding the antique wine racks and cataloguing the historic find. Although the monetary value of Liberty Hall's Madeira cannot be made public, its the largest known collection in the United States and one of the most extensive in the world.

America's original 13 colonies imported about 95 percent of Madeiran wine produced on the autonomous islands of Portugal, according to historical accounts.

"We have about six different versions of Madeira that was [drunk] because Madeira was the drink of gentleman," said Schroh, referring to the wine's earliest epoch.

Most of Liberty Hall's Madeira was stored in the attic because unlike most wine, this particular vintage needs a warm temperature, Schroh said.

The museum was contacted by The Rare Wine Co., a premier wine merchant based in California, which tested the Madeira and further explained this spirit will rarely turn to vinegar. The stateside connoisseur reached out to Liberty Hall after the museum announced its discovery.

Liberty Hall decided to fill a decanter with a sampling from one of the original casks of Madeira. Kean had a small taste, and said those who like sweet sherry wines will enjoy this aged vin.

Madeira was the best wine to ship during the 18th century because it almost never spoiled, Shcroh said.

"So you could open some of these bottles, and it might be perfect," he added.

The museum, originally constructed in 1760, was built as a country getaway by the then prominent New York lawyer, William Livingston. Livingston would go on to serve in the First and Second Continental congresses, become New Jersey's first elected governor and sign the United States Constitution.

The Kean family was the second generation to live at Liberty Hall, taking over the original estate in 1811. Multiple generations of the Keans continued to live at the estate until 1973, when the home was designated a National Historic Landmark. The family has worked to preserve and enhance the estate's invaluable character.

But the museum is far from dormant.

Thirty-three American citizens were naturalized at the historic site on June 20, and Liberty Hall kicked off an Independence Day celebration with the Consulate General of Portugal on June 23.

When members of the Kean family decided to turn their home into a museum, they chose to make each room a progression of styles dating from 1772 on, Kean explained.

The parlor dates to the Victorian era, and they are currently remodeling an upstairs bedroom to resemble the time when Alexander Hamilton stayed at the estate circa 1773, he said.

Kean's father and uncle served in World War I, so the museum's new exhibit showcases artifacts and personal memorabilia belonging to both men. A blue flag with two stars, symbolizing their military service, hangs on the museum's front entrance window.

During the wine cellar restoration process, the museum revealed the original brick flooring that had been covered by a layer of concrete, Kean said. The bottom shelf of the wooden wine rack was rebuilt in order to re-enforce the dilapidated fixture.

The demijohns -- a glass jug, and container of choice for alcohol merchants at the time -- were also encased in wooden crates for extra protection during sea voyages. When the jugs arrived, they were syphoned, rebottled, waxed, labeled and stored. Individual bottles were usually wrapped in hay in order to protect shipments charting across the Atlantic Ocean.

When Schroh started working at the museum about 20 years ago, the wine racks that lined the cellar walls were enclosed, something the Kean family probably did during the Prohibition era, he said. But the museum removed the extra wall and restored the fence-like wooden section which opens up the display space for visitors.

The museum staffers cataloged the cases and jugs of Madeira as they were discovered. While some of the stock needed to be researched online, most of the wine was still labeled with handwritten tags, or could be looked up in the thousands of Liberty Hall documents dating more than 200 years.

"We have the receipts from the liquor store, or the liquor distributor in New York, in Elizabeth or wherever," Schroh said. "We can also trace the purchaser, when it was purchased and who it was purchased from."

Part of the research showed some of the Madeira was imported by Robert Lenox, a millionaire merchant from New York who owned land in the heart of Harlem, which is where the borough's main avenue gets its name.

Until about the 1960s, the state of New Jersey kept death inventories which were compiled by local tax assessors, Schroh explained. The process evaluated a person's assets for inheritance purposes, and the museum has records from each generation who lived at Liberty Hall, which provided a road map for researching the Madeira.

"We don't have to go to England to find something, or somewhere else to find something -- it's here," said Schroh. "We just have to put all the pieces together, and that's the fun part."

David J. Del Grande may be reached at ddelgrande@njadvancemedia.com. Follow him on Twitter @SLOSONE. Find NJ.com on Facebook.