This image shows the facade of the Mission San Carlos Borromeo chapel from the left side, viewed from the courtyard. The white adobe building has been converted to the welcome center.
The description states:
SAN CARLOS BORROMEO MISSION,
Since its establishment in 1770 it has remained an outstanding link of the historic Mission Trail. At the foot of its altar rest the remains of Fra. Junipero Serra, founder of California Missions.
–Father Serra chose this as headquarters for the mission chain which reached from San Diego to Sonoma. This postcard likely dates from the 1950s.