The archaic period (6000 BC to AD 1000) up to the arrival of the Spanish brought increased hunter-gatherers to the area.

[7][8] The area between the Rio Grande and the Nueces River, which included the county, became disputed territory known as the Wild Horse Desert, where neither the Republic of Texas nor the Mexican government had clear control.

[8][11] Early settlers found Dimmit County to be an abundant grassland with mesquite, oak, and ash trees and wildlife that included buffalo, deer, turkeys, feral horses (mustangs), panthers, and javelinas.

Artesian springs, bubbling up from a vast reservoir of underground water, fed into running streams that harbored giant catfish, crawfish, and mussels.

Explorers found the area a good place to hunt mustangs, and to feed and water cattle.

[12] Pioneering cattleman Levi English settled Carrizo Springs in 1865 with a group of 15 families from Atascosa County.

King also staunchly enforced the "dry county" law once the residents voted to outlaw the sale of alcohol.

[8] Formation of the 1914 White Man's Primary Association was designed to exclude Mexican Americans from any meaningful participation in county politics.

In the 1944 Smith v. Allwright case, the United States Supreme Court found the White Primary to be unconstitutional.

[16][17] D.C. Frazier drilled the first artesian well, which produced gallons of water a minute, near Carrizo Springs in 1884.

Taylor introduced large-scale Bermuda onion and strawberry farming to the area, and was the first to use irrigation on a large scale in Dimmit County.

[19] Irrigation helped make Dimmit County part of the Texas Winter Garden region.

By 1934, the United States Department of the Interior concluded that the existing water supply would not support substantial additional development.

The oil play has improved business activity in the county, but raised fears regarding the adequacy of water supplies, as fracking requires injection of large quantities of water under pressure into wells to break surrounding rock.

[22] According to the U.S. Census Bureau, the county has a total area of 1,335 sq mi (3,460 km2), of which { 5.6 square miles (15 km2) (0.4%) are covered by water.

While the state of Texas went strongly for Republican George W. Bush in the 2004 presidential election, Dimmit County was a traditional stronghold of the Democratic Party, supporting U.S.