After the disaster of the First Battle of Manassas, the Government realized that the city of Washington, DC was in grave danger. If the city fell, the war would be over. As a result, a new series of forts, batteries, rifle trenches and other installations surrounding the city and extending across the Potomac into Virginia was begun. Eventually, there would be more than 60 forts of varying size and design. Remnants of many still remain, some of them maintained by the National Park Service.
Fort Totten was a medium-sized fort, a seven-sided polygon with a perimeter of 270 yards. It was located atop a ridge along the main road from Washington to Silver Spring, Maryland, about three miles north of the Capitol, and a half-mile from the Military Asylum or Soldier's Home, and a small cottage where President Lincoln would sometimes go to relax. The fort was of typical design for its time, with earth walls some 15 feet thick and 8 feet high. Outside the walls (or "ramparts" - remember "The Star Spangled Banner"?) was a large ditch or dry moat over seven feet deep and twelve feet wide, and outside that was a broad cleared area surrounding a barrier of tree branches, brambles and general debris (the "abattis"). Along the inner surface of the wall were gun platforms for several types of cannon, some firing over the parapet, others firing through openings in it, and a "banquette," a kind of shelf on which soldiers could stand to fire over the wall.
Inside the fort were "bombproofs," dugout chambers covered with up to 12 feet of earth, used as magazines, storehouses, and protection during attack. The soldiers' barracks, officers' quarters and mess house were outside the fort, immediately to the south.
During the war, Fort Totten was occupied by units of the 76th New York; the 2d Pennsylvania Heavy Artillery; the 136th and 137th Pennsylvania; Company A of the 4th US Artillery; the 150th Ohio national Guard; the 1st New Hampshire Heavy Artillery; and of course, parts of the 1st Vermont Heavy Artillery.
The Library of Congress holds an enormous collection of Civil War engineering drawings and photographs, including several of Fort Totten. The site is in a relatively good state of preservation today, and is maintained by the National Park Service as an adjunct to Rock Creek Park in the District of Columbia. It is a short stroll from the Fort Totten station on the Washington Metro system. I visited and photographed the site in April, 1999.
For more information about Fort Totten and the defenses of Washington, I recommend Mr. Lincoln's Forts: A Guide to the Civil War Defenses of Washington by Benjamin Franklin Cooling III and Walton H. Owen II (White Mane Publishing 1988). It is available from amazon.com and barnesandnoble.com, among other sources. The book contains some interesting quotations from Lt. Col. George Chamberlain of the 1st Vermont Heavy Artillery, under whom Benjamin Kenfield served.
For more information about Fort Totten, try the National Park Service site.
It's part of a nice site describing the Defenses of Washington on the NPS server.