The Republic of California recognized in the Treaty of Guadalupe Hildago (1848) territory in the following states to be a part of this republic : California, Utah, Wyoming, Nevada, Arizona, Colorado, New Mexico. 

The following is from the National Archives website.

This treaty, signed on February 2, 1848, ended the war between the United States and Mexico. By its terms, Mexico ceded 55 percent of its territory, including the present-day states California, Nevada, Utah, New Mexico, most of Arizona and Colorado, and parts of Oklahoma, Kansas, and Wyoming. Mexico also relinquished all claims to Texas, and recognized the Rio Grande as the southern boundary with the United States.