From the plaque:
The annunciation mosaic on the church facade is a reproduction of a detail from the image of Our Lady of the Angels in the Porciuncula chapel at Assisi. This image provided the inspiration from which the city was named to honor Nuestra Senora de Los Angeles. The mosaic was erected in 1981 to commemorate the bicentennial of the founding of the city. Presented by His Eminence Timothy Cardinal Manning, Archbishop of Los Angeles to the parishioners of La Placita and the People of the City of Los Angeles, September 4, 1981.