It was used in the American civil war by the Union cavarly but it did not replace the standard issue muzzle-loading muskets despite the Spencer's advantages.
The design of the rifle was completed by Christopher Spencer in 1860, and was for a magazine-fed, lever-operated rifle chambered for the .56-56 Spencer rimfire cartridge.
At the start of the American civil war Christopher Spencer had tried to convince the Union Army to use his rifle but his gun was used in small numbers by Union troops. However, Christopher Spencer was eventually able to gain an audience with President Abraham Lincoln, who subsequently invited him to a shooting match and demonstration of the weapon. Lincoln was impressed with the weapon, and ordered that it be adopted for production.The Spencer showed itself to be very reliable under combat conditions, with a sustainable rate-of-fire in excess of 20 rounds per minute. Compared to standard muzzle-loaders, with a rate of fire of 2–3 rounds per minute, this represented a significant tactical advantage. However the Spencer and its ammunition were expensive to produce and it did not replace the single shot muskets.
The Spencer rifle was also simpler in production and cheaper than the Henry repeating rifle, the Spencer's main competition.
The Confedarates nicknamed it the Horizontal shot tower, the Spencer proved to have the upper hand against the Confedarates muzzleloaders and although the Confedarate forces captured large numbers of Spencer rifles and carbines they could not produce the rimfire cartridge the gun fired as they didn't have the resources.
After the war Christopher Spencer went out of buisness as there was no longer large demands for his gun. Many US Army Spencer's were then sold on the surplus market to Europe and used by the Frecnh in their war against Germany in the early 1870's.