Lophophora williamsii, better known by its common name Peyote, but also sometimes called Mescal Button or the Divine Cactus, is a small, spineless cactus whose native region extends from the southwestern United States, specifically in the southwestern part of Texas, through central Mexico. They are found primarily in the Chihuahuan desert and in the state of Tamaulipas amongst scrub, especially when limestone is present in the soil. The cactus is well known for its psychoactive alkaloids and among these mescaline in particular. Certain American Indians tribes have used the plant at least since European arrival in the Americas, but likely much longer, for both medicinal and religious purposes. The plant's pink flowers emerge from March through May, and in exceptional cases as late as September.