Additional TxDOT Speed Limit Information
In addition to the previous post, the Texas Department of Transportation (TxDOT) has additional resources about speed limits. This is especially true for state highways: https://www.txdot.gov/safety/driving-laws/speed-limits.html On that first page you will see information such as:
Texas Speed Limits Database
Here is the official database from TxDOT for speed limits throughout the State of Texas: https://gis-txdot.opendata.arcgis.com/datasets/TXDOT::txdot-speed-limits/explore Once on that page, you can zoom in on the map to get more specific information about the counties of interest to you. Additionally, you can download the entire set of data if you wish.