Los Angeles (US: (listen) lawss AN-jl-s; Spanish: Los ngeles [los axeles], lit.'The Angels'), often referred to by its initials L.A., is the commercial, financial, and cultural center of Southern California. With a population of roughly 3.9 million as of 2020, it is also the largest city in the state of California and the second most populous city in the United States after New York City, as well as one of the world's most populous megacities. Los Angeles is known for its Mediterranean climate, ethnic and cultural diversity, Hollywood film industry, and sprawling metropolitan area. The city of Los Angeles lies in a basin in Southern California adjacent to the Pacific Ocean extending through the Santa Monica Mountains and into the San Fernando Valley. It covers about 469 square miles (1,210 km2), and is the seat of Los Angeles County, which is the most populous county in the United States with an estimated 9.86 million as of 2022.Home to the Chumash and Tongva indigenous peoples, the area that became Los Angeles was claimed by Juan Rodrguez Cabrillo for Spain in 1542. The city was founded on September 4, 1781, under Spanish governor Felipe de Neve, on the village of Yaanga. It became a part of Mexico in 1821 following the Mexican War of Independence. In 1848, at the end of the MexicanAmerican War, Los Angeles and the rest of California were purchased as part of the Treaty of Guadalupe Hidalgo, and thus became part of the United States. Los Angeles was incorporated as a municipality on April 4, 1850, five months before California achieved statehood. The discovery of oil in the 1890s brought rapid growth to the city. The city was further expanded with the completion of the Los Angeles Aqueduct in 1913, which delivers water from Eastern California.

Los Angeles has a diverse economy, and hosts businesses in a broad range of professional and cultural fields. It also has the busiest container port in the Americas. In 2018, the Los Angeles metropolitan area had a gross metropolitan product of over $1.0 trillion, making it the city with the third-largest GDP in the world, after Tokyo and New York City. Los Angeles hosted the 1932 and 1984 Summer Olympics and will host the 2028 Summer Olympics. More recently, statewide droughts in California have strained both the citys and Los Angeles Countys water security.

The Baldwin Hills Dam disaster occurred on December 14, 1963, in the Baldwin Hills neighborhood of South Los Angeles, when the dam containing the Baldwin Hills Reservoir suffered a catastrophic failure and flooded the residential neighborhoods surrounding it. It began with signs of lining failure, followed by increasingly serious leakage through the dam at its east abutment. After three hours, the dam breached, with a total release of 250 million US gallons (950,000 m3), resulting in five deaths and the destruction of 277 homes. Vigorous rescue efforts averted a greater loss of life.

The reservoir was constructed on a low hilltop between 1947 and 1951 by the Los Angeles Department of Water and Power, directly on an active fault line, which was subsidiary to the well-known nearby Newport–Inglewood Fault. The underlying geologic strata were considered unstable for a reservoir, and the design called for a compacted soil lining meant to prevent seepage into the foundation. The fault lines were considered during planning, but were deemed by some, although not all, of the engineers and geologists involved as not significant.The former reservoir is now part of the Kenneth Hahn State Recreation Area.