Colt's major patent on revolvers in the mid-1800s eventually expired and this allowed a plethora of arms-makers to benefit from the development and sale of similar guns heading into the American Civil War (1861-1865). Smith & Wesson jumped at the chance to provide a useful military sidearm and developed a series of relatively small, cartridge-firing guns as a result. This was of particular importance for many sidearms of the period still relied on two-piece "cap-and-ball" ammunition - the Smith & Wesson pistol fired a self-contained, single piece cartridge which protected the ammunitions contents from external influences such as weather and the environment. The gun also utilized a bored-through cylinder which was based on a patent purchased from Rollin White and these qualities immediately set the gun apart from competitors.
The series saw service in the "War Between the States" and proved an immediate success for the Union Army - to the point that Smith & Wesson could not keep up with the wartime demand.
The first offering in the series was named simply the "Model 1" and this version was intended for close-in self-defense. To keep its dimensions manageable (and its weight light), it was chambered for a .22 rimfire cartridge. The follow-up offering, the definitive "Model 2", was appropriately enlarged to fire the more useful .32 rimfire cartridge which promised better man-stopping capabilities in close quarters. Despite its larger size, the Model 2 was still compact enough to conceal-carry for the standard infantryman.
Over 77,000 examples of the gun were manufactured between 1861 and 1864. Barrel lengths of 4", 5" and 6" were eventually offered.