While US infantry forces during the Civil War had only limited access to the newest rifle technology, cavalry units adopted a wide variety of new carbines in significant numbers. Among these were a design by Benjamin Joslyn. It first appeared in 1855 designed to use paper cartridges, but by the time the US Army showed an interest Joslyn had updated the weapon to use brass rimfire ammunition. The first version purchased by the government was the 1862 pattern carbine, of which about a thousand were obtained. Many more were ordered, but it took Joslyn a couple years to really get his manufacturing facility and processes worked out. By the time he had this all straightened out, the design had been updated again to the 1864 pattern, addressing several minor problems with the earlier version. Ultimately more than 11,000 of the 1864 pattern carbines were purchased by the Union, chambered for the same .56-.52 cartridge as the Spencer carbines also in service.
Interestingly, the Joslyn also holds the place as the first breechloading weapon manufactured by the Springfield Arsenal. Three thousand breech units were purchased from Joslyn and built into complete rifles by Springfield, although they came too late to see service in the war and were ultimate sold to France, it appears.