Mathis is a city in San Patricio County, Texas, United States. The population was 4,942 at the 2010 census.In 1887, when the San Antonio and Aransas Pass Railroad was laying tracks across San Patricio County, Thomas H. Mathis received naming rights when he donated 300 acres for a townsite and school. Mathis and his brother J. M. Mathis, held 37,000 acres in the vicinity. The brothers had dropped out of the Coleman, Mathis, Fulton Cattle Company in 1879. Thomas Mathis owned an additional 60,000 acres around Mathis and built a fence enclosing the town. As late as 1906, Mathis was enclosed and arriving and departing trains had to be let in and out.Mathis' success was partially fueled by residents of Lagarto moving to be near the railroad. The Mathis post office opened in 1890 and the town's first school was held in a private residence in 1893. Two years later, a one-room school was built, and in 1913, a second railroad arrived.