Contra Costa County, California
In 1821 Mexico gained independence from Spain. While little changed in ranchero life, the Mexican War of Independence resulted in the secularization of the missions with the re-distribution of their lands, and a new system of land grants under the Mexican Federal Law of 1824. Mission lands extended throughout the Bay Area, including portions of Contra Costa County. Between 1836 and 1846, during the era when California was a province of independent Mexico, the following 15 land grants were made in Contra Costa County.
Spanish attempts to reconquer Mexico
Finally On December 28, 1836, Spain recognized the independence of Mexico under the Santa María–Calatrava Treaty, signed in Madrid by the Mexican Commissioner Miguel Santa María and the Spanish state minister José María Calatrava. Mexico was the first former colony whose independence was recognized by Spain; the second was Ecuador on February 16, 1840.