We could've built both. Five Montanas were planned, and six Midways. Montana was originally set to be laid down in 1941 along with the second unit, Ohio. Some design changes and more pressing wartime construction pushed them back, until all five (Montana, Ohio, Maine, New Hampshire, and Louisiana) were canceled on 21 July 1943. Incidentally, Japanese Naval Intelligence knew about the ships, and predicted in an estimate on 1 July 1943 that the ships would be canceled and the materials and funds used for additional carrier construction. The three Midways that were canceled were done so before they were laid down, and they were unnamed.