Alta California ceased to exist as an administrative division separate from Baja California in 1836, when the "Siete Leyes" constitutional reforms in Mexico re-established Las Californias as a unified department, granting it (in some ways) more autonomy. Most of the areas formerly comprising Alta California were ceded to the United States in the Treaty of Guadalupe Hidalgo that ended the Mexican–American War in 1848. Two years later, California joined the union as the 31st state. Other parts of Alta California became all or part of the later states of Arizona, Nevada, Utah, Colorado, and Wyoming.