El Sereno's population rose markedly as the country prepared for the war. Due to the rationing of gas and rubber, communities along the Pacific Electric routes received the majority of new residents who came to work at the aircraft and munitions factories in Los Angeles. El Sereno experienced major industrial growth during these years. Many of the families who moved here during these years were Italian-American.
The rise in population lead to the construction of the El Sereno Theatre, the third such establishment in the community. Built in 1940 at 3355 N. Eastern Avenue, the structural engineer was William Bostock.
Looking southwest across the intersection of Huntington Drive and Eastern Avenue. Seen are Ascot Hills, a service station, the Art Deco style El Sereno Theatre (later the Mazatlan Theatre), Foster and Kleiser billboards for various products, including Ten High bourbon by Hiram Walker, Coca Cola, Polly Gas, tea, and Richfield gasoline. Homes are present in the hills and railroad tracks are present on the far right. Photograph dated August 20, 1941.