Try this link:
Texas Jails Texas County Jails.
I know you won't want to drive all the way down to Gonzales from Dallas just to see the jail, but if you're ever in the neighborhood, visit the Gonzales Jail Museum. The jail was built between 1885 and 1887, and it was used until 1975. It's right on the town square, right by the courthouse, which is quite a photogenic building itself.
Here is a story about the jail: Albert Howard's hanging on March 18, 1921, was the last held in Gonzales County and this jail. A legend persists that while Howard was in jail, he became obsessed with the clock on the courthouse, keeping strict attention to the number of hours he had to live. He swore his innocence would be shown by the clock, that none of the four faces would ever keep the same time again if he was hanged. Through the years the faces have rarely been consistent.
The gallows is still there inside the jail.