Additional Information :
Long used for mining and grazing, it did not become a city of Phoenix possession until 1959, when the area was annexed and a long-term lease agreement was signed with the state of Arizona. It later became one of the major rallying points for mountain preservation efforts.
While the actual rocks of the Phoenix Mountains (including the areas around Piestewa Peak and North Mountain) are very old, the mountain shapes are, geologically speaking, quite young. They were formed about 14 million years ago as the crust of the earth was gradually stretched from northeast to southwest, elevating mountain ranges and down dropping the basins between them. Much of the area’s rock is a metamorphic type of granite known as schist. Mercury mines were worked in the area of today’s Dreamy Draw Recreation Area.