Luckily for the Apollo 13 astronauts the explosion of the Apollo space craft took place a few hours before they were to separate for the moon landing.They used the Lunar module to travel back to the earth.
Yes Apollo 13 is American history, as Apollo 13 is the only time a spacecraft has returned from deep space that is the dark side of the moon after it was damaged seriously. the side of the Apollo spacecraft had blown out.And all the three astronauts were alive.
The Apollo 13 was a big set back for N.A.S.A.as it also forced M.A.S.A to spend money to correct the spacecraft and its problems. So as their original plan was to have Apollo 20 as the last one, they were forced to end at Apollo 17..It was also a big blow to the pride of the U.s.A.
If by "traveled to" you mean "walked on", 12. If you include those who only orbited the moon and didn't land, add another 15 (three from Apollo 8, three from Apollo 10, three from Apollo 13, and 1 from each of the missions where someone did land).