The area covered by Marshall County was part of the territory set aside by the U.S. government for resettlement of the Choctaw tribe and the closely related Chickasaw tribe from their lands in the southeastern United States.

The U.S. Army built Fort Washita in 1842 to protect the new arrivals from raids by other tribes.

[3] Railroads came to the present-day Marshall County in 1901, when St. Louis, Oklahoma, and Southern Railway (acquired shortly after by the St. Louis and San Francisco Railway), known as the "Frisco," constructed a north-south line.

The following year, the St. Louis, San Francisco and New Orleans Railroad (formerly the Arkansas and Choctaw Railway) laid tracks from east to west through the area.

The State of Oklahoma relocated part of this line in 1941 to make way for the creation of Lake Texoma.

Completion of the Denison Dam in 1942 created Lake Texoma, which inundated part of Marshall County's land area and formed the current southern boundary and the eastern boundary of the county as well.

26.40% of all households were made up of individuals, and 14.50% had someone living alone who was 65 years of age or older.

[3] Oil and gas production began soon after the county was formed at statehood.

[3] Other significant business sectors are wood products, manufacturing (especially livestock trailers), and tourism.