The rocket technology necessary for such a feat underwent testing during 1961-1966. In 1966, the unmanned flights of Apollo-Saturn AS-201, AS-203 and AS-202 (in order of launch) showed the readiness of the Saturn IB launch vehicle to carry astronauts into space.
The astronauts were in training for AS-204, the first manned test of the Apollo Command/Service Module. However, on January 27, 1967, a fire on the launch pad claimed the lives of the three astronauts during a preflight test. NASA retroactively named the unflown mission Apollo 1, as the agency redesigned the Apollo command module and returned to unmanned test flights.
Following Apollo 17, three more missions, 18, 19 and 20, were planned, but cancelled owing to budget constraints. Apollo-Saturn technology was used for four Skylab missions and the Apollo-Soyuz Test Project in 1975 before NASA ended the program.