Red Oak is on Interstate Highway 35 twenty miles south of Dallas in northern Ellis County. In 1844 James E. Patton and his family settled on Red Oak Creek a few miles southeast of Billingsley Fort, at the site of present Ovilla. The first post office came to the area in 1847 from Mitchell's Branch, two miles from the site of future Red Oak. The settlement was originally called Possum Trot because of the abundance of possums in the area. It was renamed Red Oak after Ellis County was formed in 1849 for the creek. Before the Civil War the principal crop of the local farmers was wheat. In the 1860s an increase in cotton production occurred because more slaves came to the area from other southern states. Cotton was still produced in 1988, although farming was not central to the local economy.
James E. Patton also founded the first church in the area, the Shiloh congregation of the Cumberland Presbyterian Church, on July 25, 1847. Other churches, including the Baptist and the Methodist, were founded at cemeteries. In 1884 the Missouri, Kansas and Texas Railroad reached Red Oak. The townspeople did not want the trains to disturb the tranquility of the community, so the tracks passed by a mile northwest. The line was finally finished in 1890, connecting Red Oak with Dallas and Waco. The town eventually moved out and centered along the railroad. Fires in 1909 and 1919 caused extensive damage first to the southern and later to the northern part of town. Red Oak was incorporated in 1949. The population was 350 in 1950 and 1,882 in 1980. In 1967 Red Oak was used as the site for three days of filming for the motion picture Bonnie and Clyde. A local woman, Mrs. Mabel Cavitt, made a brief appearance as Bonnie Parker's mother. In 1987 Red Oak had an estimated 2,425 residents, most of whom were commuters to Dallas or Fort Worth. In 1990 the population was 3,124. The population grew to 4,301 in 2000.