For Arkansas Data:
A starting place to search for Arkansas data is at the website for the Center of Advanced Spatial Technologies (CAST) of the University of Arkansas. Its URL is http://www.cast.uark.edu/

For Mississippi Data:
The Mississippi Automated Resource Information System (MARIS) is the first site to check for Mississippi data. Its URL is http://www.maris.state.ms.us/

For Texas Data:
The Texas Natural Resources Information System (TNRIS) is the first site to check for Texas data. Its URL is http://www.tnris.state.tx.us/