This is a great historic map collection housed at the UT library in Austin.
http://www.lib.utexas.edu/maps/historical/history_texas.htmlI enjoy researching the Barvarian exodus to central Texas in the mid-1800's. The Germans sent excellent cartographers forward of the imigrants to plot land for settlement.
A great example of this is the 1849 map entitled
Karte des Staates Texas
It shows the layout of New Braunfels which is a town my ancestors helped settle.