Robertson County is named for Sterling C. Robertson, who received a colonization grant from Mexico. On December 14, 1837, the First Texas Congress passed a measure establishing Robertson County from portions of Milam, Bexar, and Nacogdoches counties and naming it in honor of Sterling Robertson. When the county was organized the following year, the settlement of Franklin (usually referred to as Old Franklin today to differentiate it from the present county seat also named Franklin), which served as headquarters for surveyors of a land district including present Leon, Freestone, Limestone, Navarro, and other counties, became the county seat. Over the next nine years sixteen counties were carved from its original jurisdiction, and the county only assumed its present limits in 1846. In 1850 the county residents voted to move the county seat from Old Franklin to Wheelock because the town was closer to the most heavily populated areas of the area. Six years later the county seat was once again moved, this time to a new town, Owensville, near the geographical center of the county, where it remained until after the Civil War.qv During the mid-1830s Robertson County was the scene of numerous battles between Anglo-American settlers and Indians. Among the most famous was the May 19, 1836, attack on Fort Parker during which Cynthia Ann Parker, mother of Chief Quanah Parker, was taken captive. The Indian raids, however, began to abate after 1838, when a company of Texas Rangers commanded by Eli Chandler was stationed at Old Franklin. By the time Texas joined the United States in 1846, the frontier had pushed farther west, and Indian raids in Robertson County had become infrequent.
During the 1840s the number of settlers increased slowly; as late as 1850 the population was only 934. But during the next decade numerous new settlers arrived to take advantage of the fertile bottom land along the Brazos and Navasota rivers. In just ten years, from 1850 to 1860, the population grew more than five-fold, surging to 4,997. Most of new residents were from the Old South, and many of them brought their slaves with them. During the same decade the slave population grew from 264 to 2,258. By 1860 40 percent of the county's families owned one or more slaves, and two of the state's largest slaveholders, B. F. Hammond and Reuben Anderson, each of whom owned 100 or more slaves, lived in the county. The first farms in the county were on the upland prairies, but as the population increased and the Indian threat abated growing numbers of settlers moved into the bottomlands. Between 1835 and 1840 a number of large land owners, including Andrew Cavitt, Liston Purdy, Joseph Webb, and James R. Robertson, established plantations in the Brazos Valley. Although cotton was grown as early as 1840, during the decade of 1840s subsistence farming continued to be the rule. But by the early 1850s a thriving plantation economy, based largely on cotton, had begun to emerge. Between 1850 and 1860 the cotton crop increased from 429 to 6,467 bales. The last antebellum decade also witnessed a tripling in corn production, and a five-fold increase in the value of livestock. On the eve of the Civil War Robertson County was in most ways typical of the counties of the region, decidedly Southern in character and outlook, with an rapidly developing plantation economy. Not surprisingly given the large number of slaveholders, the county residents staunchly supported the Southern cause, and nearly 85 percent (391 of 467) of those who went to the polls cast their votes in favor of secession. Robertson County's men also volunteered for the Confederate army in large numbers. Company C, Fourth Texas Regiment, Hood's Texas Brigade, which fought at Gaines Mill, Second Manassas, the Wilderness, Gettysburg, and Chickamauga, was largely recruited in Robertson County.