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
Samuel Colt development when he dismissed an idea from one of his gunsmiths, Rollin White. White had an idea of a "bored-through" revolver cylinder to allow the use of metallic cartridges in a handgun. After Colt fired White for suggesting an improvement to his revolver, White took his idea to Colt's competitor, Smith & Wesson, who patented his invention and kept Colt from being able to build cartridge firearms for almost 20 years. Colt purchased a large tract of land beside the Connecticut River, where he built his first factory in 1848, a larger factory called the Colt Armory in 1855, a