Apollo 2 & 3 (Unmanned Test Flights)
Before the Apollo 1 disaster, three unmanned test flights of Apollo to Saturn rockets took place. Missions AS-201, AS-202 and AS-203 took place in 1966, testing the Saturn 1B launch vehicle. They set the stage for AS-204 which was planned to be the first manned mission but ended up killing three astronauts.
That mission was renamed later as Apollo 1. Apollo 4 was to be next, but the plan was to continue the unmanned test flights as NASA redesigned the command module.
The next three unmanned Apollo flights aren’t well known…