Father Juan Crespí picked the spot for Mission Vieja because water was available at what is now called the Whittier Narrows.

[2][3][4][5][6] Father Angel Somera and Father Pedro Cambon, both Franciscan missionaries, founded Mission Vieja, the original Mission San Gabriel Arcangel, on September 8, 1771; the location is today near the intersection of San Gabriel Boulevard and the Rio Hondo River.

The Juan Matias Sanchez Adobe, built in 1844, still stands at the center of old Rancho la Merced in East Montebello.

[10] The earliest reported San Andreas Fault earthquake in California was on July 28, 1769, at the future site of the Mission Vieja.

The earthquake was recorded by members the Portolá Spanish expedition charting a land route from San Diego to Monterey.