Bastrop County is located on the Colorado River near the west margin of the Gulf Coastal Plain. Its principal mineral resources are clay, lignite, sand and gravel, petroleum, and surface and underground water. The Missouri, Kansas, and Texas and the Southern Pacific railroads cross the county. Its public road system includes Highways Nos. 20 and 71, and lateral roads. The elevation on the Colorado River at the west county line approximates 375 feet, and at the east county line 275 feet. The elevation of the upland is from 350 to 600 feet.