The peninsula is divided into two parts:
- The northern part is the State of Baja California. To avoid confusion, this state is often referred to as "Baja California Norte".
- The southern part, below 28°N, is the State of Baja California Sur.
- 1690s-1700s: Spanish settlement in California
- 1804: The Spanish colony of California is divided into Alta ("high") and Baja ("low") California at the line separating the Franciscan missions in the north from the Dominican missions in the south.
- In 1850, after Alta California has been annexed by the United States to become the US state of California, Baja California is further divided into northern and southern territories.
- 1952: Northern Baja California becomes the 29th state of Mexico.
- 1974: The southern territory becomes the 31st state, Baja California Sur.