Trinidad is on the St. Louis Southwestern Railway and Farm Road 1667, fifteen miles west of Athens in western Henderson County. Settlement of the area began before 1840, when O. M. Airhart ran the local ferry across the Trinity River, which was originally called the Trinidad River, and Zach Smith operated a ferry four miles north of the present townsite. By 1844 the town recorded a general store and a saloon. It became known as Trinity Switch, for its location on the Trinity River, when it became a station on the St. Louis Southwestern in 1880. When residents applied for a post office in 1880, the name Trinidad was chosen (instead of Trinity Switch) to avoid duplication with another post office with the same name. Records suggest, however, that the Trinidad post office was not actually opened until 1891. In 1910 five businesses and a population of seventy were reported. The population remained small until the 1920s, when Texas Power and Light opened a plant on the Trinity River, and a Lone Star Producing Company plant began manufacturing chemical fertilizer there. The 1930 population of 750 had decreased to 550 by 1940, when sixteen businesses were reported in the community. In 1990 Trinidad reported 1,056 residents. The population reached 1,091 in 2000.