Three main tributaries - the West, Elm, and East forks - feed the Trinity from headwaters in North Texas. Discovery of prehistoric Malakoff Man carved stone heads near this site in the 20th century revealed that humans inhabited the Trinity valley thousands of years ago. Indian villages dotted the river banks when European exploration began. French explorer Robert Cavelier Sieur de La Salle called this waterway the River of Canoes in 1687. Spaniard Alonso de Leon is credited with first using the name "Trinity" in 1690.
The fertile Trinity floodplain drew Anglo-American settlers to this area during the Republic of Texas. Buffalo, first Henderson County Seat, was founded a few miles upstream at a ferry crossing. Navigation of the Trinity has been proposed in a number of ambitious plans since the 1850s. Steamboats plied the river carrying cotton, cattle, and lumber to Galveston and other Gulf of Mexico ports until the 1870s. Arrival of the railroad ended the era of riverboat trade.
Founded in 1881 on the St. Louis Southwestern Railroad, also known as the Cotton Belt, the town of Trinidad had a pump station to draw water for the boilers of steam locomotives. A ferry crossed the Trinity here until a bridge was erected in 1900.