Digital History Reader, U.S. Railroad Construction, 1860–1880 (页面存档备份,存于互联网档案馆) Virginia Tech, Retrieved August 21, 2012. "Total Union railroad miles" aggregates existing track reported 1860 @ 21800 plus new construction 1860–1864 @ 5000, plus southern railroads administered by USMRR @ 2300.
Digital History Reader, U.S. Railroad Construction, 1860–1880 (页面存档备份,存于互联网档案馆) Virginia Tech, Retrieved August 21, 2012. "Total Union railroad miles" aggregates existing track reported 1860 @ 21800 plus new construction 1860–1864 @ 5000, plus southern railroads administered by USMRR @ 2300.