Ralph A. Wooster's book 'Lone Star Regiment in Gray' [ISBN 1-57168-546-4] page 108 has a brief reference that may help; to wit:

". . . Col. Middleton T. Johnson, the first commander of the Fourteenth Cavalry, . . . The men under his command came largely from north central and east Texas."

My great grandfather, Sgt. James R. Box, Co. B, 14th Texas [Dismounted] Cavalry, lived in / enrolled in Rusk County; east Texas.

A search of the Texas Confederate Pension records [Texas State Library and Archives Commission] yields an application [number 05399] for a Thomas Hardin, Hill County. I suggest you request the application; they are inexpensive. http://www.tsl.state.tx.us/arc/archmail.html

Lastly, the compiled regimental records from the National Archives often contain soldier's age at, date of, and place of enrollment. I gather the Dallas Public Library has the microfilm for Texas regiments; there are other sources.

jack r. box
boulder, colo