The Lexington-class aircraft carriers were a trio of carriers operated by the US Navy from 1926 to 1946. Originally designed as a class of six battlecruisers following WWI, growing interest in naval aviation, and the abortive Washington Naval Treaty of 1921 compelled planners to come up with a design for the USN's first fleet carriers. Three of the ships - Lexington, Saratoga, and Constitution (renamed Concord) were converted to carriers based on this design.