His varied career included working for railroad and mining companies, and service as a mayor and a legislator.

[1][a] His father served in the 13th Indiana Cavalry Regiment as a lieutenant and died of disease during the war[3] or from wounds he received.

Cook moved to Leadville, Colorado, in 1880 and became division superintendent of the Denver & Rio Grande Railroad.

[1] He suspended railroad service and organized a group to save 100 miners who were trapped in the Homestake mine by a snowslide near Leadville.

During another winter storm when people began to starve, he hired 1000 miners to clear the railroad tracks so that Leadville could receive food shipments.

He became an independent mining operator in 1893 and became senior vice commander in chief of the Grand Army of the Republic in 1905 and 1906.