The Spencer repeating rifle was a manually operated lever-action

Lever-action

Lever-action is a type of firearm action which uses a lever located around the trigger guard area, to load fresh cartridges into the chamber of the barrel when the lever is worked. Most lever-action firearms are rifles, but lever-action shotguns and a few pistols have also been made...

, repeating rifle

Repeating rifle

A repeating rifle is a single barreled rifle containing multiple rounds of ammunition. These rounds are loaded from a magazine by means of a manual or automatic mechanism, and the action that reloads the rifle also typically recocks the firing action...

 fed from a tube magazine

Magazine (firearm)

A magazine is an ammunition storage and feeding device within or attached to a repeating firearm. Magazines may be integral to the firearm or removable . The magazine functions by moving the cartridges stored in the magazine into a position where they may be loaded into the chamber by the action...

 with cartridges. It was adopted by the Union Army

Union Army

The Union Army was the land force that fought for the Union during the American Civil War. It was also known as the Federal Army, the U.S. Army, the Northern Army and the National Army...

, especially by the cavalry

Cavalry

Cavalry or horsemen were soldiers or warriors who fought mounted on horseback. Cavalry were historically the third oldest and the most mobile of the combat arms...

, during the American Civil War

American Civil War

The American Civil War was a civil war fought in the United States of America. In response to the election of Abraham Lincoln as President of the United States, 11 southern slave states declared their secession from the United States and formed the Confederate States of America ; the other 25...

, but did not replace the standard issue muzzle-loading rifled musket

Rifled musket

The term rifled musket or rifle musket refers to a specific type of weapon made in the mid-19th century. Originally the term referred only to muskets that had been produced as a smoothbore weapon and later had their barrels rifled...

s in use at the time. The Spencer carbine was a shorter and lighter version.
The design was completed by Christopher Spencer

Christopher Miner Spencer

Christopher Miner Spencer was an American inventor, from Manchester, Connecticut, who invented the Spencer repeating rifle, one of the earliest models of lever-action rifle, a steam powered "horseless carriage", and several other inventions...

 in 1860, and was for a magazine-fed, lever-operated rifle chambered for the 56-56 Spencer rimfire

Rimfire ammunition

A rimfire is a type of firearm cartridge. It is called a rimfire because instead of the firing pin of a gun striking the primer cap at the center of the base of the cartridge to ignite it , the pin strikes the base's rim....

 cartridge.