界限街
A second line opened on November 15, 1862. It was built along 7th Street NW from N Street NW to the Potomac River. In 1863 the 7th Street line was extended north to Boundary Street NW. It expanded south to the Arsenal (now Fort McNair) in 1875. A third line, built by 1870, ran down 14th Street NW from Boundary Street NW (now Florida Avenue) to the Treasury Building.