On January 4, 1970, NASA announced the cancellation of Apollo 20 so that its Saturn V could be used to launch the Skylab Space Station as a "dry workshop" (assembled on the ground), instead of constructing it as a "wet workshop" from a spent upper stage of a Saturn 1B launch vehicle. Also,budget restrictions had limited the Saturn V production to the original 15. NASA Deputy Administrator George M. Low announced that the final three Moon landings were rescheduled for 1973 and 1974, following the three planned Skylab missions.

Another lunar landing was lost in April 1970 when Apollo 13 had its inflight failure, and the Fra Mauro landing site was reassigned to Apollo 14. Then on September 2, 1970, NASA announced it was cancelling the H4 and J4 missions, due to more budget cuts. Skylab was also pushed out to 1973, and
the final landing schedule became:

Apollo 15 (J1) Hadley Rille, July 1971
Apollo 16 (J2) Decartes Highlands, April 1972
Apollo 17 (J3) Tarus Littrow Valley, December 1972

At the time, 35 of NASA's 49 active astronauts were waiting for a chance for a mission.
In the closing days of the program, Apollo 17 LMP Harrison Schmitt aggressively lobbied for a manned landing on the far side of the moon, targeting the lava-filled farside Tsiolkovskiy. Schmitt's ambitious proposal included the launch into lunar orbit of special communications satellites based on the existing TIROS satellites to allow contact with the astronauts during their powered descent and lunar surface operations. NASA administrators rejected these plans based on lack of funding and added risk.

In August 1971, President Richard Nixon even proposed to cancel all remaining lunar landings (Apollo 16 and 17). His Office of Management and Budget (OMB) Deputy Director Casper Weinberger was opposed to this, persuading Nixon to keep the remaining Moon missions, but recommended that if such cancellation would happen that it be "on the ground that Apollo 15 was so successful in gathering needed data that we can now shift, sooner than previously expected, to the Space Shuttle, Grand Tour, NERVA.

Note: With later Apollo Missions, one can look at the facts and look at the required specialised missions concerning military operations. One can also respect the need for secrecy for such missions.
However, at this point one can suspect the process of disinformation, whereby one does not know what is the truth and what is not. Questions are asked 'Did these later missions take place with reference to Apollo 18-20? (We now verge onto the Pseudo Science section concerning these later Apollo Missions, the debate contiues and are recorded as a matter of record).

NASA contracted to have 15 flight-worthy Saturn Vs produced. Apollo 11 achieved the first landing with the sixth Saturn V, leaving nine for follow-on landings. The following landing sites were chosen for these missions, planned to occur at intervals of approximately four months through July 1972.

Apollo 12 (H1) Nov. 1969, Ocean Of Storms (Surveyor 3 site)
Apollo 13 (H2) April 1970, Fra Mauro Highlands
Apollo 14 (H3) Littrow Crator
Apollo 15 (H4) Censorinus Crator

The last 5 missions were J-class missions using the Extended Lunar Module, capable of three-day stays on the Moon and carrying the lunar rover:

Apollo 16 (J1) Decartes Highlands
Apollo 17 (J2) Marius Hills
Apollo 18 (J3) Copernicus Crater
Apollo 19 (J4) Hadley Rille
Apollo 20 (J5) Tycho Crater (Surveyor VII site)

As the later missions were up to three years out, little detailed planning was made, and a variety of landing sites were given for some flights. According to "NASA OMSF, Manned Space Flight Weekly Report" dated July 28, 1969, Apollo 18 would have landed at Schroter's Valley in February 1972, Apollo 19 in the Hyginus Rille region in July 1972, and Apollo 20 in Copernicus crater in December 1972.

Other proposed landing sites and schedules for the last three missions included Gassendi Crater (Apollo 18, July 1973), Copernicus (Apollo 19, December 1973), and Marius Hills or Tycho crater (Apollo 20, July 1974).

As a number of ambitious Apollo Aplication Programmes were planned, it was still hoped in 1969 that further Saturn V launch vehicles could be contracted, allowing for more ambitious lunar missions.In the NASA report "Scientific Rationale Summaries for Apollo Candidate Lunar Exploration Landing Sites" from March 11, 1970, Apollo 18 is targeted for Copernicus, and Apollo 19 is assigned Hadley Rille (the eventual landing site of Apollo 15). The Apollo 20 mission had been canceled two months before, but the report still suggested its target, Hyginus rille, possibly as an alternative Apollo 19 landing site.