The Appalachian Plateaus form the northwestern-most province of the Appalachian Mountains, stretching from New York southwest to Alabama. They are composed of sedimentary rocks including sandstones, conglomerates, and shales deposited during the late Paleozoic. These rocks exist largely as horizontal beds that have been cut by streams to form the mountainous terrain that is distinctive today. Mountain ranges existing in the Appalachian Plateaus include the Catskill, Pocono, Allegheny, and Cumberland Mountains.