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 Model 1855 Sidehammer Pocket Revolver purchased the National Arms Company in 1870. Actual original Colt models subsequent to the Sidehammer and inheriting a solid frame and a spur trigger were the Colt House (1871) and the Colt New Line (1873). The revolving mechanism of the cylinder was also used by Colt's in the following long arms, in rifle and carbine configurations: Colt Model 1855 Sidehammer Pocket Revolver The Colt Model 1855 Sidehammer, also known as the Colt Root Revolver after engineer Elisha K. Root (1808–1865), was a cap & ball single-action pocket revolver used during the American Civil War and made by the Colt's Patent