Los Angeles Building and Construction Boomed in the Early 1900s

The city of Los Angeles stayed within its initial 30 square-mile area until the 1890s. The earliest large enlargements to the city were the districts of Highland Park and Garvanza to the north, and the South Los Angeles region. In 1906, the approval of the Port of Los Angeles and a change in state law enabled the city to annex the Harbor Gateway, a thin strip of land leading from Los Angeles towards the port. San Pedro and Wilmington were incorporated in 1909, and the city of Hollywood was added in 1910, bringing the city up to 90 square miles. Also annexed that year were the cities of Colegrove and Cahuenga, as well as part of Los Feliz.

The establishment of the Los Angeles Aqueduct gave the city with 4 times as much water as it needed, and the offer of water service became a powerful lure for nearby communities. The city locked in customers through annexation by refusing to supply other communities. By referendum of the residents, 170 square miles of the San Fernando Valley were annexed to the city in 1915, almost tripling its area. Over the next two decades dozens of new annexations brought the city's area to 450 square miles. Currently, it is approximately 470 square miles.

In World War II, Los Angeles grew as a locus for production of war supplies and munitions. Thousands of African Americans and white Southerners relocated to the city to take factory jobs.

By 1950, Los Angeles was an industrial and financial giant created by war production and migration. Los Angeles assembled more cars than any city other than Detroit, produced more tires than anywhere but Akron, and stitched more clothes than any city except New York. Additionally, it was the national center for the production of films, radio programs and TV shows. Building and construction greatly expanded as tract houses were built in suburban communities financed by the Federal Housing Administration.

Los Angeles continued to spread out, particularly with the development of the San Fernando Valley and the construction of the freeways launched in the 1940s. When the local streetcar line went bankrupt, Los Angeles became a city built around the motorcar.