In 1837, with Texas Revolutionary hostilities essentially ended, Robertson resigned his Texas commission and returned to Kentucky, where he married Mary Elizabeth Cummins. He returned with his wife and several relatives to Texas in December 1837, buying land and settling in Washington-on-the Brazos. He established a medical practice, and became known on the frontier as an Indian fighter through six years of sporadic campaigning. He also served in the military forces that helped repel two invasions by the Mexican army in 1842. After stints as the town's coroner, mayor, and postmaster, Robertson built a home in Independence in 1845. By this time, the Republic of Texas was on the verge of becoming the State of Texas. Robertson was elected in 1847 to the Texas House of Representatives and in 1849 to the Texas State Senate.