Trinity Mills was on Farmers Creek two miles northwest of Carrollton in northwest Dallas County. The site was on the original land grant of A. W. Perry. It was settled in 1853 and named for a gristmill owned by Wade H. Witt and A. W. Perry. The two-story rock structure was built in the late 1840s and was powered by oxen on a treadwheel. A local post office was established in 1858 and was discontinued and reopened four times before its termination in 1915. By 1860 James M. Kennedy had become a full partner in Trinity Mills, which also had a store.
In 1878 the Dallas-Wichita Railroad was constructed through Trinity Mills, and the community subsequently developed as a cattle-shipping center. Three years later it had a general store, a physician, a druggist, and twenty-six farmers. By 1884 the community had a population of 150, two churches, a school, and a Western Union telegraph office. Six years later Trinity Mills had a population of fifty, a nursery, a mineral-water dealer, a safe business, and a farm import business. By 1915 the community had declined to two stores, and in 1930 the population stood at thirty-five. Trinity Mills subsequently became part of Carrollton.