Ok, this trail is technically in that state just south of Oklahoma. It's just a good swim from the state line via the wide Red River and Lake Texoma. Cross Timbers 50M/Marathon is one of the oldest trail races in the state of Texas, and uses this trail system.
This website gives a good history of the Cross Timbers trail, has some camping info, and a good map.
I love this map. Doesn't it make you wanna go play there?