Ford did not build 'all of the B-24s' at Willow Run, but they built not quite half of the total production. A total of 18,432 B-24s were produced by all sources.
The first completed B-24 came off the assembly line at Willow Run on May 15, 1942. On June 28th, 1945 production Run ceased - 8,685 planes had been manufactured.