Morton County, North Dakota: Early history
The county was created on January 8, 1873, by the Dakota Territory legislature, using territory that had not previously been included in any county. The county organization was not completed at that time, but the new county was not attached to any other county for administrative or judicial matters. Its organization was completed on November 5, 1878. It was named for Oliver Hazard Perry Throck Morton (1823-1877), governor of Indiana during the American Civil War and later a United States Senator. Portions of the county were partitioned off on February 10, 1879, causing the county organization to be not fully organized. This lasted until February 28, 1881, when the organization was again completed. The county's boundaries were adjusted in 1881 and in 1887. In 1916, a portion of Morton County was partitioned off to create Grant County, setting Morton County's boundaries to their present configuration.
After the Northern Pacific Railroad announced the location for the western approach to its Missouri River bridge, a new settlement appeared in December 1878. Initially the US Post Office designated the riverside settlement "Morton" after the corresponding county. The Morton post office later moved to the city center 3 miles west. The county was reorganized in 1881 after the detached land was returned to Morton County by the 1881 legislature. The town, eventually renamed Mandan, was named the county seat.