The Trinity has been identified as the stream that the Caddo Indians called “Arkikosa” in Central Texas and “Daycoa” nearer the coast, as well as the one that Réne Robert Cavelier, Sieur de La Salle called “River of the Canoes”, in 1687. Domingo Ramón in 1716 incorrectly applied the name Trinity to the river known as the Brazos River until he actually reached the Trinity and was told by the Indians that other Spaniards called that stream the Trinity. The Marqués de Aguayoqv and other later explorers used the name Trinity consistently.

The Trinity River has four forks: The Clear Fork, the Elm Fork, the West Fork, and the East Fork:

The West Fork flows eastward through the city of Fort Worth while the Clear Fork flows northeastward through Fort Worth; the two forks meet near downtown Ft. Worth.

The Elm Fork flows south from near Gainesville, Texas and east of the city of Denton.

The Elm Fork and Clear Forks merge as they enter the city of Dallas form the Trinity River proper.

The East Fork of the Trinity River rises in central Grayson County and flows south seventy-eight miles, through central Collin, western Rockwall, eastern Dallas, and western Kaufman counties, to the southwestern part of Kaufman County, where it joins the West Fork.

The Trinity then flows southeastward through eastern Texas and then southward, into the Trinity Bay, an arm of Galveston Bay, and inlet of the Gulf of Mexico, east of Houston.

During the colonial period of Texas history, the land along the lower course of the Trinity was settled as far up as Anderson County. The Anahuac disturbances were among the most historically significant events of the era. Settlement up the Trinity valley continued to advance rapidly in the period of the republic. Beginning about 1836 numerous packet boats steamed up the Trinity River, bringing groceries and dry goods and carrying down cotton, sugar, cowhides, and deer skins. One of the largest of these early steamers was the Scioto Belle, put in service in 1844. Some of the packets penetrated as far as Magnolia, ten miles west of Palestine, and in 1854 one reached Porter's Bluff, fifty miles below Dallas. Often their movements were impeded by snags or sand bars or halted by low water.

Following a convention on Trinity improvement in 1849 at Huntsville, in 1852 Congress authorized a survey of the river. In the next year an army engineer's report mentioned the Trinity as the deepest and least obstructed river in Texas, stating that seven steamboats were in operation in its lower channel, and estimated that navigation was practicable. Under a Texas act of 1858 a bar was removed from the river's mouth.

Navigation fell off during the Civil War, but the river was considered a point of vulnerability by the Confederacy and patrols were made by local militia units to keep it secure. After the war, in 1868, navigation began again and Job Boat No. 1 reached Dallas with a cargo, after a voyage of a year and four days from Galveston. In the years before 1874 nearly fifty boats continuously navigated the river as far north as Trinidad in Kaufman County and Porter's Bluff in northern Navarro County.

In the peak season of 1868-69 boats carried 15,425 bales of cotton down the Trinity. With the construction of railroads to Dallas in the early 1870s the river traffic began to die. But high railroad rates and the prospect of Dallas as a major port kept the dream of a navigable Trinity River alive. Since that time numerous schemes to make the Trinity navigable have been proposed. Several proposals received considerable attention, and some construction was undertaken, but the dream of a port of Dallas has never been realized. Major flooding occurred on the Trinity River in the years 1844, 1866, 1871, and 1890, but a major event in the spring of 1908 set in motion the harnessing of the river. On 26 May 1908, the Trinity River reached a depth of 52.6 feet and a width of 1.5 miles. Five people died, 4,000 were left homeless, the Texas & Pacific Railroad bridge at Dallas was destroyed and property damages were estimated at $2.5 million, a huge amount of money at that time. Old newspaper articles concerning the history of the Trinity region in the 19th century and early 20th centuries can be found on Jim Wheat's History page HERE.