1925 - Palomar Ballroom in Los Angeles

Famous as the birthplace of the Swing movement, when Benny Goodman started a nation wide craze with a radio broadcast in 1935.

Wikipedia entry

The Palomar Ballroom, built in 1925, was a famous ballroom in Los Angeles, California, in the United States. It was destroyed by a fire on October 2, 1939.
Opened: 1925
Architectural style: Spanish Colonial Revival architecture
Destroyed: October 2, 1939
Seating capacity: 10,000
Former names: El Patio Ballroom, Rainbow Gardens