It was here in Old Town that Saint Junípero Serra celebrated his First Holy Mass in California on July 2, 1769, near the site of the present Immaculate Conception Church, and it was on the hill overlooking Old Town that he planted the cross which marked the site of the Mission and the Presidio.

In 1849, the first parish church was established in Old Town with the name of Immaculate Conception and was dedicated in 1858. It still stands and is known as the Old Adobe Chapel on Conde Street. The cornerstone to the present Immaculate Conception Church was laid in 1868 under the direction of Father Antonio Ubach. With the population swing toward the south, it was not until July 6, 1919, that the church was dedicated by Archbishop John J. Cantwell of Los Angeles.