Mexia is at the intersection of US 84 and Hwys 14 and 171, twelve miles northeast of Groesbeck in northeastern Limestone County. It was named for the Mexa family, who in 1833 received an eleven-league land grant that included what is now the townsite.

Oil and natural gas discoveries led to a boom for Mexia in the 1920's, but the boom went bust in the 1930s, when the Great Depression forced many people to leave in search of work.

The number of residents in the town stabilized at 6,500 in the early 1930s, but the number of businesses reported fell from 280 to 190. In 1942 a camp for prisoners of war was established at Mexia; the facility was converted in 1947 for use as the Mexia State School, which became one of the community's principal employers. The population was reported as 6,618 in the early 1950s, 5,943 in the early 1970s, 7,172 in the late 1980s, and 6,933 in 1990.