On transcontinental trail of California Gold Rush. Until 1846 a part of Bexar Land District, Republic of Texas. Private tracts were surveyed as early as 1847. German Emigration Company colony (90 mi. SE) had grants here, but in 1840s found Indians blocking settlement. Butterfield Overland Mail managers lived at stands in area, 1858-61. R. F. Tankersley family established a permanent home in 1864 in future Tom Green County. By 1874 there were five settlements here, including Bismarck Farm, a colony of 15 German immigrants. The county (12,756 sq. mil., 10½ times as large as state of Rhode Island) was created in 1874 and named for heroic Gen. Green (1814-64), a state official and gallant Texas soldier.
After a decade of progress, the original Tom Green County began losing outlying areas. Midland County — halfway between Fort Worth and El Paso on newly opened Texas & Pacific Railway — was created in 1885. Settlers remote from San Angelo petitioned for new counties in 1887, and the Texas Legislature created Crane, Loving, Upton, Ward and Winkler. Coke and Irion Counties were cut out of Tom Green in 1889. Ector and Sterling were created in 1891. Last diversions — Glasscock (1893) and Reagan (1903) — gave Tom Green its present size. It remains influential in the region.