The Niagara Escarpment is a long escarpment, or cuesta, in the United States and Canada that runs predominantly east/west from New York State, through Ontario, Michigan, Wisconsin and Illinois. It is composed of the Lockport geological formation of Silurian age, and is similar to the Onondaga geological formation, which runs parallel to it and just to the south, through western New York and southern Ontario. The escarpment is most famous as the cliff over which the Niagara River plunges at Niagara Falls, for which it is named.