Brown County, near the geographic center of Texas, is bordered on the north by Eastland County, on the west by Coleman County, on the south by McCulloch and San Saba counties, and on the east by Comanche and Mills counties. The center of the county lies at 31°45' north latitude and 99°00' west longitude, sixty-five miles southeast of Abilene. The county is named for Capt. Henry Stevenson Brown, a company commander in the battle of Velasco, a delegate to the Convention of 1832, and one of the first Anglo-Americans in the area.

The county was formed on the western frontier in 1856 from Comanche and Travis counties and organized in 1858, with Brownwood designated as the county seat; the town was also awarded the county's first post office that year with Wiley B. Brown as postmaster. In 1860 the United States census found 244 people living in the county, none of them slaveholders. The census also counted 2,070 cattle in the area, and ninety-one acres of land was classified as "improved." The county developed slowly between its founding and the 1870s, primarily because conditions were not secure for settlement until the late 1870s or early 1880s, as settlers were harassed by Indians and white predators for twenty years after the county was formed.

Development of the county was accelerated in the 1890s and early 1900s when two railroads built tracks into the area, providing a stimulus to area farmers and helping maintain an atmosphere favorable to experiments in crop diversification. The Fort Worth and Rio Grande Railway reached the county in 1892; the Gulf, Colorado and Santa Fe line built into Brownwood in 1895, and by 1903 had extended its tracks to Menard. The new railroad connections helped Brownwood to prosper, since the absence of railroad facilities in southern Eastland and Callahan counties led farmers from those areas to Brownwood to do their marketing.