1972 saw humanity's last manned mission to the moon of the 20th century, Apollo 17.
 This was also the final flight of the Saturn V rocket, and its only night launch.
"Apollo 21" is an apocryphal reference to an eleventh manned Moon landing mission of NASA's Apollo program.
 Apollo contracted for the construction of fifteen Saturn V launch vehicles used to launch the Apollo spacecraft to the Moon, and achieved the first manned landing with the sixth one (Apollo 11), leaving nine for follow-on lunar missions, through Apollo 20.
 However, budget cuts caused NASA to cancel the last three missions, ending the lunar program after Apollo 17.
 One Saturn V was used to launch the Skylab space station, and parts of the other two became museum displays.
The Command/Service Module (CSM) was one of two spacecraft, along with the Lunar Module, used for the United States Apollo program which landed astronauts on the Moon.
 It was built for NASA by North American Aviation.
 It was launched by itself on three suborbital and low Earth orbit Apollo test missions using the Saturn IB launch vehicle.
 It was also launched twelve times on the larger Saturn V launch vehicle, both by itself and with the Lunar Module.
 It made a total of nine manned flights to the Moon aboard the Saturn V.
Saturn V Dynamic Test Stand, also known as Dynamic Structural Test Facility, at the George C. Marshall Space Flight Center in Huntsville, Alabama is the test stand used for testing of the Saturn V rocket and the Space Shuttle prior to the vehicles' first flights.
 Designated building 4550, it stands 363 ft tall and is 98 ft square.
 NASA built the test stand in 1964 to conduct mechanical and vibrational tests on the fully assembled Saturn V rocket.
 Major problems capable of causing failure of the vehicle were discovered and corrected here.
The Saturn V (spoken as "Saturn five") was an American human-rated expendable rocket used by NASA between 1967 and 1973.
 The three-stage liquid-fueled super heavy-lift launch vehicle was developed to support the Apollo program for human exploration of the Moon and was later used to launch Skylab, the first American space station.
 The Saturn V was launched 13 times from the Kennedy Space Center in Florida with no loss of crew or payload.
 As of 2017,  the Saturn V remains the tallest, heaviest, and most powerful (highest total impulse) rocket ever brought to operational status, and holds records for the heaviest payload launched and largest payload capacity to low Earth orbit (LEO) of 140000 kg , which included the third stage and unburned propellant needed to send the Apollo Command/Service Module and Lunar Module to the Moon.
Skylab was the United States' first space station, orbiting Earth from 1973 to 1979, when it fell back to Earth amid huge worldwide media attention.
 Launched and operated by NASA, Skylab included a workshop, a solar observatory, and other systems necessary for crew survival and scientific experiments.
 It was launched unmanned by a modified Saturn V rocket, with a weight of 170000 lb .
 Lifting Skylab into low earth orbit was the final mission and launch of a Saturn V rocket (which was famous for carrying the manned Moon landing missions).
 Skylab was not simply a place of habitation; massive science experimentation was undertaken there.
 When data from these experiments (some of which were on physical film) were returned to Earth, analysis of scientific and engineering data of each mission was completed.
 Skylab's solar observatory was one of its major functions.
 Solar science was significantly advanced by the telescope, and its observation of the Sun was unprecedented.
 As the Skylab program drew to a close, NASA's focus had shifted to the development of the Space Shuttle, through which NASA hoped to reduce the cost of space access compared to previous launch systems.
The Saturn V Instrument Unit is a ring-shaped structure fitted to the top of the Saturn V rocket's third stage (S-IVB) and the Saturn IB's second stage (also an S-IVB).
 It was immediately below the SLA "(Spacecraft/Lunar Module Adapter)" panels that contained the Lunar Module.
 The Instrument Unit contains the guidance system for the Saturn V rocket.
 Some of the electronics contained within the Instrument Unit are a digital computer, analog flight control computer, emergency detection system, inertial guidance platform, control accelerometers and control rate gyros.
 The instrument unit (IU) for Saturn V was designed by NASA at Marshall Space Flight Center (MSFC) and was developed from the Saturn I IU.
 NASA's contractor to construct the Saturn V Instrument Unit was International Business Machines (IBM).
The Saturn C-5N was a conceptual successor to the Saturn V launch vehicle which would have had a nuclear thermal third stage instead of the S-IVB used on the Saturn V.
 This one change would have increased the payload of the standard Saturn V to Low Earth orbit from 118,000 kg to 155,000 kg.
Saturn V Dynamic Test Vehicle, designated SA-500D, is a prototype Saturn V rocket used by NASA to test the performance of the rocket when vibrated to simulate the shaking which subsequent rockets would experience during launch.
 It was the first full-scale Saturn V completed by the Marshall Space Flight Center (MSFC).
 Though SA-500D never flew, it was instrumental in the development of the Saturn V rocket which propelled the first men to the Moon as part of the Apollo program.
 Built under the direction of Dr. Wernher von Braun, it served as the test vehicle for all of the Saturn support facilities at MSFC.
The ST-124-M3 is a device for measuring acceleration and attitude of the Saturn V launch vehicle.
 It was carried by the Saturn V Instrument Unit, a 3 ft , 22 ft section of the Saturn V that fit between the third stage (S-IVB) and the Apollo spacecraft.
 Its nomenclature means "stable table" (ST) for use in the moon mission (M), and it has 3 gimbals.

Question: Saturn V delivered men to the Moon for the last time, in which NASA mission?
Answer: Apollo 17