L.A. is the most populous city in California, the second most populous city in the United States, after New York City, and the third most populous city in North America. It is the largest city on the West Coast of North America and has nearly four million inhabitants.

Los Angeles suffers from air pollution in the form of smog. The Los Angeles Basin and the San Fernando Valley are susceptible to atmospheric inversion, which holds in the exhausts from road vehicles, airplanes, locomotives, shipping, manufacturing, and other sources. The smog season lasts from approximately May to October. While other large cities rely on rain to clear Smog.