Republic of Baja California
The Republic of Lower California, also known as the Republic of Baja California, was a proposed state from 1853 to 1854, after American private military leader William Walker failed to invade Sonora from Arizona. Walker wanted to appropriate Sonora, and his claims had both the support of tycoons and government complacency in the United States.
Source: Wikipedia — Republic of Baja California (CC BY-SA 4.0)