Migration is supposedly voluntary. However, there is a history of involuntary migration. The original 44 multiracial settlers of Los Angeles were most probably forced to migrate to the newly found El Pueblo de la Reyna de Los Angeles in 1781. In 20th century, Japanese American were evacuated and incarcerated during the WWII. Soon after as they were returning home to Los Angeles, in the early 1950s hundreds of Mexican American families were evicted from Chavez Ravine to build affordable housing for the poor that never actually happened.
However, for the most part people migrated here because Los Angeles was a very desirable city. After the independence of Mexico from Spain in 1821, Los Angeles attracted people from parts of Mexico, America, and Europe. Los Angeles started gaining importance. By 1841 the population in this pueblo had almost tripled to 1680. With the arrival of the Santa Fe railroad in 1885, migration was at a full gallop as real estate developers, railroad companies, and other commercial interests advertised Los Angeles as a land of sunshine and temperate climate. Wealthy chilled Easterners and Midwesterners coming to spend winters here found themselves in love with Los Angeles, started building residences, and made the city their home. People also believed that this climate could cure chronic diseases like consumption and flocked to the sanitariums that cropped up in Southern California in the late 19th and early 20th century.
People continued to migrate throughout the 20th century for sunshine, temperate climate, and job opportunities in film, oil, automobile, and airplane industry, and a piece of California dream.