The document discusses the history of the Columbia Turnpike, including its origins as a turnpike built in 1810 to connect Washington D.C. to areas to the southwest. It played an important role during the Civil War as a route south. In the early 20th century, the turnpike was the site of experimental road maintenance programs by the US Department of Agriculture. Several prominent structures were later built along the turnpike, including the Pentagon in the 1940s, which dramatically changed the area.