
What's the oldest opera house in Los Angeles
The Merced Theater is one of the oldest buildings in Los Angeles for the performing arts. They started accepting audiences in 1871. The theater was built by William Abbot for his wife Maria Merced Garcia.
http://www.lasangelitas.org/buildings.htm
It has been the center of the theatrical activity in 1871 until 1876 but as more theater opened the Merced Theater begun to feel its decline in 1876.

