1878 Camp Grierson's Spring is established as a subpost of Fort Concho and named in honor of Col. Benjamin H. Grierson.
1903 Reagan County is carved from Tom Green County and named for United States Senator John Henninger Reagan. Stiles, named after local rancher William G. Stiles, becomes the first county seat.
1924 Boom town community of Best plunges into vice and violence, necessitating the Texas Rangers intervention. The Rangers destroy buildings that are being used as brothels, gambling houses, and saloons.
1925 Voters move the county seat to Big Lake.
1926 Texon is established by the Big Lake Oil Company for its employees and their families and is devoted to family life.
According to the U.S. Census Bureau, the county has a total area of, of which are land and is covered by water. The Spraberry Trend, the third-largest oil field in the United States by remaining reserves, underlies much of the county.
As of the census of 2000, there were 3,326 people, 1,107 households, and 872 families residing in the county. The population density was. There were 1,452 housing units at an average density of. The racial makeup of the county was 64.64% White, 3.01% Black or African American, 0.54% Native American, 0.27% Asian, 29.56% from other races, and 1.98% from two or more races. 49.49% of the population were Hispanic or Latino of any race. There were 1,107 households out of which 46.80% had children under the age of 18 living with them, 68.10% were married couplesliving together, 7.20% had a female householder with no husband present, and 21.20% were non-families. 19.80% of all households were made up of individuals and 7.50% had someone living alone who was 65 years of age or older. The average household size was 2.96 and the average family size was 3.42. In the county, the population was spread out with 34.20% under the age of 18, 7.60% from 18 to 24, 28.10% from 25 to 44, 19.90% from 45 to 64, and 10.30% who were 65 years of age or older. The median age was 32 years. For every 100 females there were 100.50 males. For every 100 females age 18 and over, there were 100.50 males. The median income for a household in the county was $33,231, and the median income for a family was $36,806. Males had a median income of $31,228 versus $18,750 for females. The per capita income for the county was $13,174. About 9.30% of families and 11.80% of the population were below the poverty line, including 10.60% of those under age 18 and 23.60% of those age 65 or over.
