The M115 203 mm howitzer, also known as the M115 8 inch howitzer, was a towed howitzer used by the United States Army. Until the 1950s it was designated the 8 inch Howitzer M1. The original design started in 1919 but lapsed until resurrected in 1927 as a partner-piece for a new 155 mm gun. It was standardised as 8 inch Howitzer M1 in 1940. The M115/M1 was towed by the M35 Prime Mover gun tractor or a Mack 7⅓ ton 6x6 truck. The first photos of the M115 type 8 inch cannon on its redesign carriage appeared in 1931, but development was slowed by the Great Depression.