Den Otter, Philosophy of Railroads, 170-73.
For Mexico, Pletcher, Rails, Mines, and Progress, 34-93.
Bensel, Yankee Leviathan, 243-48.
Oberholtzer, Jay Cooke, 2: 381-97.
CPH to Hopkins, March 10, 1870, LB, 2:96, CPH to Hopkins, March 19, 1873, LB, 4: 27, box 21, Hopkins Collection.
Cooke to Puleston, Sept. 1, 1871, Northern Pacific, Letters no. 1 (LB), Jan. 19, 1870 - Sept. 27, 1871, Private Letters, Cooke Papers.