Call it America's first earmark.

On July 5, 1776, the new independent Continental Congress in Philadelphia spent 600 pounds to purchase 96 acres along the Delaware River in Gloucester County.

The strategic bluff on the river bank became Fort Billingsport. For a month in 1777, American troops held off the British navy as it tried to sail upriver to Philadelphia. The fort was taken out of military service in 1815.

Nowadays, the overgrown landmark in Paulsboro is located inside the fence of an oil refinery's tank farm. Local preservationists want to study the site before the refinery's owners proceed with expansion plans.

That needs to happen.

Earmarks - individual projects authorized by Congress - carry a negative connotation these days for their wasteful spending. But Fort Billingsport was an early effort to protect what was then the national capital 15 miles upstream. As such, local history buffs are referring to the site as "the birthplace of homeland security."

An ordinary patch of ground can yield a valuable history lesson that can't ever be replaced. Just consider the excavation of a passageway for slaves at the President's House on Independence Mall. It became such a surprise attraction that a new, modified plan for a memorial to open in 2009 should become the first national site commemorating the lives of slaves.

Fort Billingsport, by comparison, is believed to be the first purchase of land by the national government, and may offer a glimpse into the birth and early defense of the nation.

That's why New Jersey officials and the refinery owners, Pacific Atlantic Terminals L.L.C., should work together on a careful archaeological study of the site. But Pacific Atlantic officials haven't allowed outside archaeological experts access to the spot. Nor have they responded to requests from preservationists.

The company did issue a statement saying that a survey indicates that the proposed expansion "does not encroach on the site where the earthen fortification is thought to have existed."

Maybe so. But the Department of Environmental Protection needs to step in to determine the location of the old fort, and what remains. The agency's historical preservation office can order an archaeological survey if necessary. That could help evaluate whether the old fort can be restored enough to turn into a visitor attraction, or unearth any artifacts.

The fortification is also the first example of military engineering by Thaddeus Kosciuszko, a Polish patriot who went on to design other installations.

Paulsboro may have a compelling archaeological story waiting to be told. The opportunity to make that history come alive won't come again.