On Seventh Street at the corner of Constitution Avenue, across the street from the National Archives and beside the Sculpture Garden, is a strange column. It looks very old and must have had some function at one time. Do you know what it is?

Joan King, Washington

Washington is like an armed camp these days, with checkpoints and gun-toting guards all over the place. Security is especially tight around the U.S. Capitol. We may think this is a modern necessity, but the Capitol needed protection in the 1820s, too.

And from whom did it need protection?

Goats and sheep. And cows. Oh, and hogs, too.

The crumbling column at Seventh and Constitution is a remnant of a fence that once encircled the Capitol and was built to prevent wandering farm animals from munching on grass and ornamental shrubs.

That column is nowhere near the Capitol now, and neither are the others that you can find along Constitution Avenue and elsewhere in the city. But near the Capitol is where they started out. They are fence posts, also known as piers. The sandstone columns stood at intervals and were connected by wrought iron bars that enclosed the Capitol's 221/2 acres of grounds.

They were designed by Charles Bulfinch, the accomplished Boston architect charged with rebuilding the Capitol after it was torched by the British in 1814.

It was Bulfinch who put the first dome on the Capitol. He also designed two gatehouses that stood at the western entrance to the Capitol. The piers and the gatehouses were fashioned from the same Aquia Creek sandstone from Stafford County that was used to build the Capitol and the White House.

In the 1870s, the Capitol's grounds were enlarged, and landscape architect Frederick Law Olmsted was invited to redesign them. Bulfinch's fence was suddenly in the middle of things. The gatehouses and piers were removed in 1874.

Some of the piers were placed on Constitution Avenue (then called B Street) in 1880; the gatehouses are at 15th and 17th streets. For a while, the piers served their original purpose, holding up a fence that ran on the Mall side of the street. Other surviving fence piers are in Fort Totten Park and at the entrance to the National Arboretum.

The piers and the gatehouses are quite handsome in their unassuming way. The have features -- a rusticated treatment on the piers, a swirl of leaves over the gatehouse doors -- that are found in the Capitol.

As any good architect would, Bulfinch extrapolated features to select "the design elements he would then use in the garden structures in order to produce harmony between the locations," said Bill Allen, architectural historian at the Office of the Architect of the Capitol.

"They're sort of nice, like an English folly on a great estate in a country house in England," said Gary Scott, the National Park Service's chief historian for the National Capital Region.

Until recently, the gatehouses were used by the National Park Service to store lawnmowers, fertilizers and the like. But once it was discovered that the interiors were coated with lead paint, they were locked up tight.

The columns and houses look a little forlorn. Sandstone isn't the most durable building material. That's why the Capitol was painted. And that's why when the Capitol was enlarged, marble was used instead.

The exterior of the Capitol doesn't bear much of Bulfinch's original touch. But we still have the gatehouses and the piers.

"I view them . . . as very interesting relics of the Capitol's history that I'm very happy were saved," said Bill Allen. "So many things were just literally tossed away, and indeed some of these gateposts were tossed away. But not all of them. They saved some. I think it's very good that they did. Otherwise we would just know these from photographs."

E-mail: answerman@washpost.com.

Architect Charles Bulfinch designed this sandstone fence pier, left, and fetching little gatehouse, above, for the Capitol grounds. They were removed in 1874 and placed along what is now Constitution Avenue NW.