Colt Walker of Texas had been the major purchaser of the early Paterson Holster Pistol (No. 5 model), a five shot cal .36 revolver, and Samuel Walker became familiar with it during his service as a Texas Ranger. In 1847, Walker was engaged in the Mexican-American War as a captain in the United States Mounted Rifles. He approached Colt, requesting a large revolver to replace the single-shot Aston Johnson holster pistols then in use. The desired .44-.45 caliber revolver would be carried in saddle mounted holsters and would be large enough to dispatch horses as well as enemy soldiers. The Colt Walker
Colt Single Action Army and sold to the civilian market. The largest group of U.S. Colt Cavalry revolvers was inspected by David F. Clark, his D.F.C. cartouche being encountered on revolvers inspected from 1880 to 1887. During 1893, the .45 U.S. Colt Single Action Army revolver was retired by the Cavalry and replaced by the .38 caliber Colt Model 1892 Double Action Army revolver. The .45 Single Action Army revolver was still standard issue to the Infantry, Artillery and other branches of the U.S. Army. In 1895–1896, the U.S. federal government returned 2000 SAA revolvers to Colt to be refurbished; 800 were issued to