The Predecessor : 3-inch M1917
The 3-inch M1917 was the US Army's first dedicated anti-aircraft gun, entering service during World War I. Only a few were built, as the similar 3-inch M1918 on a mobile mount was considered more useful and was produced in large numbers.
Development of the M1917 started in 1915, and as the name implies, took two years to enter service. The gun was essentially an unmodified 3-inch M1903 (76.2 mm L/55) coastal-defense gun on a new mount allowing it to be aimed to high elevations. A number were used during the war. In the immediate post-war era it was developed as the 3-inch M3, using a removable barrel liner. In 1928 it was further improved in the 3-inch M3 by using a thicker removable liner that eased manufacturing.
Read more about this topic: 3-inch Gun M1918