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
William Mason (Colt) known as the .45 Colt. The revolver was chosen by the Army in 1872, with the first order shipping in the summer of 1873 for 8000 revolvers. After the success of the Colt Single Action Army and Colt's conversion of existing percussion revolvers to Richards-Mason conversions, Mason went on to design Colt's smallest revolver, "The New Line" in 1874. There were 5 variants, each differing in size and caliber, but all using a breechblock designed by Mason. While Colt had first developed the concept of a "double-action" revolver as early as 1857 and a patent was filed, it was never