OverviewSP Crater is a classic cinder cone in the San Francisco volcanic field, which is located in the desert region north of the San Francisco Peaks between Flagstaff, Arizona and the Grand Canyon. If you didn't know any better you might think your were on the moon. Although it is only about 800 feet from its base, being a cinder cone, it is steep and scree-covered, making the ascent a bit more arduous.
At only 71,000 years old, it is quite young in geological time. The last eruption in this area was only about 1000 years ago (source). Leading away from the cinder cone on its north side is a large black lava flow about 4 miles long that looks impressive from the rim of the crater. Apparently, the initials S.P. stand for "Shit Pot", because whoever named it thought it to be a suitable name (source). At the top you can peer into the deep crate, or even venture in a little bit if you're feeling wild.
Perhaps the best part of this cone (unless you're a geologist) are the views that can be had from the top of the Grand Canyon and more spectacularly, the San Francisco Peaks. Maybe the second best part is the quick "skiing" descent that has the descender taking giant leaps in the sandy scree, sliding every which way and occasionally tumbling until the base is reached in about 3.72 minutes, leading a person to contemplate whether it's worth the 30-45 minutes to climb to the top again just to descend once more.
Getting ThereFrom Flagstaff, take 89 North out of town for about 27 miles to milepost 446. Just before Hank's Trading Post, you will turn left off the highway onto a dirt road. I believe all this land is still owned by the Babbits but they allow public access, so be respectful (as always). You will be able to see the near-perfect cone that is SP immediately, so just head towards it, branching left at the forks except for the last one where you branch right to park near the base of the cone.
Red TapeThis whole area is part of the Babbit ranch, but they allow public access, so just don't bother their cows and be respectful.
CampingI can find no information saying that it is illegal to camp near SP crater, but neither have I found anything saying that it's legal. It is private property, so I would recommend not doing so. There are no camping facilities in the area nor any water sources.
External LinksSome information on the geology of the cone
History of the Babbitt Ranches, which owns the land.