FISHKILL, N.Y.—Ed Spaeth was researching his family tree when he discovered an 18th-century ancestor likely was buried in the woods just down the hill from his Hudson Valley home.

Although he can’t pinpoint Francois Martin-Pelland’s grave, historical evidence has led Spaeth to the nearby grove believed to be the final resting place of hundreds of other Revolutionary War soldiers posted here when Fishkill was the main supply source for Gen. George Washington’s northern army.

Today, commercial development has whittled the wooded parcel down to about 12 acres hemmed in by roads, a shopping mall, a gas station and a Mexican restaurant. A group of preservationists, history buffs and civic leaders has mustered in this Dutchess County town to try to save what could be the nation’s single largest-known burial site of Revolutionary War soldiers.

“They didn’t fight and die for this cause just to have a mall built on top of them,” said Spaeth, a 64-year-old retired school librarian.

From 1776 until 1783, the Fishkill Encampment and Supply Depot was a bustling military post. Several thousand Continental Army regulars and militiamen toiled year-round, carrying out the logistical tasks that allowed America’s first army to fight. Many, perhaps more than 1,000, died and were buried in the depot’s cemetery, 60 miles north of New York City.

The Fishkill depot’s complex of huts, barracks, storehouses and workshops was known to have included a cemetery during the war. But its exact location wasn’t confirmed until the fall of 2007, when an archaeological survey conducted for the property’s owner found several old graves in a wooded area across from the Dutchess Mall, built in the 1970s.

At the recommendation of state archaeologists, another study was done last year. Ground-penetrating radar indicated several hundred grave sites in the southern tip of the property.

“We really don’t know how many are there,” said Douglas Mackey, an archaeologist for the state Office of Parks, Recreation and Historic Sites.

Backed by the latest findings, town officials and preservationists are seeking government funding to buy the land and protect it from development. One idea is to turn the site into the first national Revolutionary War cemetery. Some have taken to calling the Fishkill site “New York’s Valley Forge.”

“This is the founding of our country,” said Mara Farrell of Fishkill Historical Focus. “There’s so much about this site that needs to be revealed.”

Retired Army Col. James Johnson , a 1969 graduate of the U.S. Military Academy and a former military history professor there, notes that the closest the Fishkill depot came to fighting was when a British force ventured up the Hudson River from Manhattan and burned a nearby village. Nevertheless, the food, clothing and armaments the depot provided to Washington’s soldiers helped them keep the redcoats from gaining control of the strategic Hudson Highlands.