Edward Moody McCook (June 15, 1833 – September 9, 1909) was born in Steubenville, Ohio. He moved to Colorado in 1848 and then to the Kansas Territory in 1849, where he became a lawyer and a Kansas legislator, serving in the territorial House of Representatives in 1859. With the onset of the Civil War, McCook traveled to Washington, D.C. and served for a time as a secret agent for the Federal government, gathering information of value to the military. He then joined the volunteer army as a captain in the 2nd Indiana Volunteer Cavalry, rising to the rank of colonel by the middle of 1862. McCook commanded a cavalry brigade at the Battle of Perryville and a division at Chickamauga. On April 27, 1864 he was promoted to brigadier general of volunteers and given command of the First Cavalry Division in the Army of the Cumberland. His 3,600 cavalrymen raided and severed the Macon & Western Railroad in late July 1864 while serving under George Stoneman during the Atlanta Campaign. On July 30, McCook was thoroughly defeated by Confederate cavalry under Joseph Wheeler at the Battle of Brown's Mill near Newnan, Georgia, losing a great number of men, horses, and artillery. McCook and his remaining cavalry marched to Tennessee to assist in the Franklin-Nashville Campaign.

In March and April of 1865, McCook commanded the First Division in Wilson's Raid and at the Battle of Selma, where the Federal cavalry dealt a crushing defeat upon Nathan Bedford Forrest. McCook's division was then assigned to re-establish Federal control and authority in Florida, and by May 13, Col. George Washington Scott surrendered the last active Confederate troops in the state. On May 20, General McCook read Abraham Lincoln’s Emancipation Proclamation during a ceremony in Tallahassee as his jubilant troops raised the U.S. flag over the state capitol, officially ending slavery in Florida.

In 1866, McCook resigned from the army and returned to civilian life. President Andrew Johnson appointed him to serve as the U.S. Minister to the Kingdom of Hawaii from 1866 through 1868. In 1869, he helped organize the Colorado Territory and was twice appointed governor by President Grant. During his tenure, Governor McCook signed the legislation that created what is now Colorado State University and was among the first state governors to endorse women's suffrage. He was a member of the Republican National Committee in 1872. McCook left the governorship when his second term expired in 1875 and turned to various business pursuits. McCook died in Chicago, Illinois, and is buried in Union Cemetery in Steubenville. The city of McCook, Nebraska was named in his honor.