William, Sam Colt's first revolver was the .36 caliber Patterson Revolver, a five shooter. It was named for Patterson, NewJersey? or NewYork?, where the plant was. Next was the Colt Walker,.44 cal., I believe, devolped with the help of a Texas Ranger and named for him. Next were the Dragoon pistols, 1st, 2nd and 3rd models. All were .44 caliber. Next followed a few "pocket" pistols based on the Dragoons, these were .32 or .36 caliber. Then came the Colt Navy model 1851, .36 caliber. The Army liked it as well, but wanted a bigger caliber, so the 1860 Army was developed. The 1861 was the same pistol as the 1860, but in .36. The 1862 was a five shooter pocket pistol. After the War, several folks were converting percussion pistols to cartride. Many used the 1860 frame. Not to be out done, Colt developed the 1872 Open Top. Similar to the 1860, this was not a conversion although it did appear similer. It was just a pistol to keep the publics interest while the final work on the 1873 Peacemaker was developed. It was chambered in .44 Colt. The next year, the venerable Single Action Army, Model 1873 was introduced. The caliber. .45 Colt, was brought about as an answer to the Smith and Wesson .45 American used in their Model three revolver, being looked at by the Army. If I missed anything, folks, please jump in and point it out!