Mark W. Summers, Railroads, Reconstruction, and the Gospel of Prosperity: Aid under the Radical Republicans, 1865-1867 (Princeton: Princeton Univ. Press, 1984), 170-71.

Jay Cooke to Brother Harry, March 20, 1870, Northern Pacific, Letters no. 1 (LB), Jan. 19, 1870 - Sept. 27, 1871, Private Letters, Cooke Papers.