Col.Henry E. McCulloch's regiment was mustered into the Texas State Troops as the 1st Texas Cavalry, or 1st Texas Mounted Rifles. This unit consisted of five under strength companies that were to patrol between the Colorado River and Red River.

The 1st Texas Cavalry, Texas Mounted Rifles was the predecessor to Col. McCord's Frontier Regiment also known as the 46th Texas Cavalry, C.S.A. In March 1861, the 1st Texas Cavalry, also known as the 1st Texas Mounted Rifles, was recruited and organized under a 12 month enlistment from several central Texas counties. On March 25, 1861, Col. McCulloch turned over the command of the 1st Texas Mounted Rifles to Capt. Thomas C. Frost and McCulloch went to San Antonio and begin recruiting for the Frontier Regiment, also known as the 46th Texas Cavalry, C.S.A. The 1st Texas Mounted Rifles was disbanded at Fort Mason on April 15, 1862 which was the expiration date of enlistments.

A total of 1,000 soldiers in ten companies, Co.A through Co.K,(there was no Co.J),were mustered into Col. McCord's Frontier Regiment, C.S.A. Requirements for enlistment were: Age 18-45, good rider and marksman, good moral character,no professional gamblers, and no habitual drunkards.

The recruits were organized into companies as follows:
Co. A..Comanche County
Co. B..Bexar County
Co. C..Bosque County
Co. D..Gonzales County
Co. E..Bell County
Co. F..Bexar County
Co. G..Travis County
Co. H..Rusk County
Co. I..Burleson County
Co. K..Lamar County

When the 1st Texas Mounted Rifles was discharged at Fort Mason in April 1862, most of those men reenlisted in the 8th Texas Cavalry Battalion.