By the end of October, the monarchs that are east of the Rocky Mountains migrate to Mexico. Many thousands from the Great Lakes region pass through Point Pelee National Park. They migrate to the sanctuaries of the Mariposa Monarca Biosphere Reserve in the Mexican states of Michoacán and Mexico. Most of the monarchs that are west of the Rocky Mountains do not travel all the way down to Mexico. Instead, they overwinter (spend the winter) in many places in central and southern California.