After leaving the Army, Sheldon entered the mercantile business in Pope County, Illinois.

After spending his last year in Illinois at Chicago, Charles Sheldon moved to Groton in Brown County, Dakota Territory because of the health of his son, James.

Sheldon entered politics in 1886, when he represented the twelfth legislative district in the Territorial Legislature.

In 1890, Sheldon was chairman of the Day County delegation at the state Republican convention in Mitchell, South Dakota.

Sheldon gave his last speech at Deadwood on October 15, 1898, and died of pneumonia five days later, with his wife and son at his bedside.