Late in 1906 the Army began to seek a 0.45 calibre semi-automatic pistol to replace it's supply of revolvers that were in service. At the same time, John M. Browning had begun designing semi-automatic pistols for the Colt company, and began working on designs that would fit the requirements of the U.S. Army. His initial designs were adopted under the M1911 moniker, and were later massproduced in the millions by Colt, Remindgton-UMC, Savage, Springfield Armoury, and other companies. Today the 1911 is arguably the most popular pistol in the world.
Colt 1911 on Wikipedia