Clockwise from the southeast, they are New Mexico, Arizona, Utah and Colorado. Where these 4 states touch is, surely coincidentally, also not far from the center of the Anasazi world and Aztlan. The region is spectacularly beautiful. mjh
Q: Where is the Four Corners Monument?
Where the 4 states meet. Seriously, it is off of US 160 on part of the Navajo Reservation (Dinetah).
Many people delight in straddling the divisions between the states. I don’t recommend it as your destination in the area, but if you happen to pass it on the way to more interesting places, you may enjoy it (I didn’t). Close by are Hovenweep and Navajo National Monument, among many others. mjh