The Trinity River was discovered in 1690 by General Alonzo de Leon while searching for an outpost, St. Louis. General de Leon discovered a river at a point near present day Midway, Texas on May 19,1690 and named the river La Santisima de la Trinidad (which means in Spanish 'The Most Holy Trinity'). It was a custom of the time to name prominent landmarks for religious feasts or holy days. The Trinity was discovered two days before the Feast of the Most Holy Trinity. 
 General de Leon would be surprised to know the river and its basin he discovered in 1690 would, almost 300 years later, contain more than 20% of the State's population of more than 21,000,000 and contain a river basin area larger than nine of the states within the United States. The Trinity River is 715 miles long. It has its beginning in four forks - the East Fork in Grayson County, the Elm Fork in Montague County, the West Fork in Archer

County and the Clear Fork in Parker County. The Clear and Elm Forks join the West Fork in Fort Worth and Dallas respectively. The East Fork joins the Trinity on the border of Ellis and Kaufman Counties just below Dallas County. From there, it flows into Trinity Bay - the northernmost part of Galveston Bay near Anahuac. 

The Authority, a political subdivision of the State, was created by an Act of the 54th Legislature in 1955.  We were charged with the following functions:

- Maintaining a Master Plan for Basin-wide development;
- Serving as a local sponsor for federal water projects;
- Providing services authorized by the Texas Legislature
within the Authority's territory.

The organization is governed by a Board of Directors who are appointed by the Governor with the advice and consent of the Senate.