The Cholla Cactus Garden is located just off Pinto Basin Road, halfway between Twentynine Palms to the north and Cottonwood to the south on the west side of the road. If you are passing through Joshua Tree National Park on this route - which is recommended if you are traveling to or from San Diego - you should take a short break here, because here you can experience unique desert vegetation up close like no other place. Otherwise, the southern section of the park offers little that is worth seeing, making the stop a pleasant change.
The reason why cacti have settled here in particular is due to the special soil conditions. The Pinto Basin was formed by tectonic shifts that caused the opposing tectonic plates to move apart, forming this lower-lying basin. Originally covered with a shallow lake, it dried up in a warmer climate period. The two mountain ranges that bound the Basin - the Pinto Mountains to the north and the Hexie Mountains to the south - were originally much higher and contributed to the silting up of the Basin through their erosion. The loose and water-permeable gravel and sand soil at the foot of the Hexie Mountains is now the ideal breeding ground for cacti.