Photograph by Stephen St. John, NGS

Blair House (1651 Pennsylvania Avenue N.W.; unpublished number)

Built in 1824, this townhouse was later home to Montgomery Blair, the lawyer who represented Dred Scott in a case that became a focal point in the slavery issue. Here Robert E. Lee was offered command of the Union Army, which he turned down in favor of the Confederate forces. In 1950-52, during the White House renovation, Harry Truman narrowly escaped an assassination attempt by Puerto Rican nationalists. Blair House, across the street from the White House, has been the official presidential guest house since 1943. It is not open to the public, but there are interesting plaques describing the Truman episode.