The name Joshua Tree was given by a group of Mormon settlers who crossed the Mojave Desert in the mid-19th century. The shape of the tree reminded them of a Biblical story in which Joshua reaches his hands up to the sky in prayer. The tree-like plant is native to the southwestern states of California, Arizona, Utah and Nevada, where they are found organically in the Mojave Desert between 1,800-5,900 feet elevation. One of my favorite plants - they look like a cross between a Palm tree and a Yucca plant.
Joshua Trees are a protected species in the Mojave Desert, so it is illegal to dig them up and carry them away.