William Crooks was a Colonel during the American Civil War, member of the Minnesota House of Representatives, U.S. Military Academy graduate, and a veteran railroader. He led the 6th Regiment Minnesota Volunteer Infantry from August 1862 to October 1864, mainly contending against the Sioux. Crooks built the first rail line in the State of Minnesota, the St. Paul & Pacific. His first locomotive he named for himself the William Crooks 4-4-0 and began its operation in 1861. His operation was taken over by James J. Hill. The William Crooks would become the first locomotive of Hill's Great Northern Railroad.

The 6th Minnesota Infantry Regiment was an infantry regiment that fought in the Union Army during the American Civil War. The 6th Minnesota Infantry spent much of the war in the Northwest fighting Dakota Indians rather than participating in the battles with the Confederacy. Led by William Crooks, the regiment saw action in the American Civil War mainly with the Dakota Tribe.