Historical markers are used to interpret, promote, and protect historic and cultural resources. Requests for markers are initiated through local county historical commissions and approved through the Texas Historical Commission (THC). The Texas Department of Transportation (TxDOT) Traffic Operations Division (TRF) works with the THC to approve markers placed on TxDOT right-of-way. TxDOT provides advance and directional guide signs for all historical markers on TxDOT right-of-way outside of city limits on conventional highways.