[5] Lands assigned to the Choctaw and Seminole tribes extended into the area now occupied by Dewey County.

Under the Reconstruction Treaties of 1866 the Choctaw and Chickasaw ceded their western domain to the United States.

[6] Dewey County was created in Oklahoma Territory in 1891 and was opened to non-Indian settlement on April 19, 1892.

Truck farmers in the eastern part of the county grew tomatoes, watermelons, apples, blackberries, and other small fruits.

Livestock (cattle, horses, mules, sheep and goats) raising had become important by the 1930s.

[6] Mineral extraction included oil and gas production (mainly in the 1940s and 1950s), bentonite, gypsum, clay and sand.

In 2000, Dewey County had only two manufacturing businesses that employed more than ten people.