 The actual gristmill was powered by oxen on a treadwheel and housed in a late-1840s two-story rock structure built on Farmers Creek, northwest of Carrollton.In 1858, a post office was established in the area which was subsequently shut-down and reopened four times before it finally closed permanently in 1915.In 1878 the Dallas-Wichita Railroad was built through Trinity Mills and the community began to emerge as a cattle-shipping center.