The Texas Association of Counties offers a map of Texas counties, cities and highways on its website. The map shows county boundaries and has inserts to show some of the largest Texas cities in greater detail. City maps for the lower Rio Grande area are also available.
From the main page of the Association's website, click on the Texas Counties, Cities and Highways map. A PDF of the map will appear in your browser. You can zoom in on all sections of the map with the Adobe magnification tool. Seven insert maps for the more populous Texas cities also appear outside of the county map.