I take this account from Harold Holzer, Lincoln at Cooper Union: The Speech That Made Abraham Lincoln President (New York: Simon & Schuster, 2004), 60-65.
For the system before the Civil War see, James E. Vance, Jr., The North American Railroad: Its Origin, Evolution, and Geography (Baltimore: Johns Hopkins University Press, c. 1995), 1-124.
This and the discussion that follows is from William R. Siddall, "Railroad Gauges and Spatial Interaction," Geographical Review 59 (Jan. 1969), 29-57.
Vance, North American Railroad, maps 114-15.
George Rogers Taylor and Irene D. Neu, The American Railroad Network, 1861-1890 (Cambridge: Harvard Univ. Press, 1956), 11-14, 35-41, 53-54.
This argument while largely true had a caveat. A freight car on a long haul route would not be switched just once but potentially would be switched every one hundred miles or so at each divisional point.
William Z. Ripley, Railroads: Rates and Regulation (New York: Longmans, Green and Co., 1916), 101-103.
George H. Miller, Railroads and Granger Laws (Madison: University of Wisconsin Press, 1971), 109.
Kamm, "The Civil War Career of Thomas A. Scott," 69-71.