Monrovia is a city located in the foothills of the San Gabriel Mountains within the San Gabriel Valley of Los Angeles County, California. It is the fourth-oldest general-law city in Los Angeles County and the larger Los Angeles Basin. Incorporated in 1887, Monrovia has evolved significantly since its founding as a sparse community of orange ranches into a residential city.
According to the 2020 census, Monrovia has a population of 37,931 residents. The city's development from its agricultural origins reflects the broader transformation of the Los Angeles region during the late 19th and 20th centuries, as rural areas progressively became suburban residential communities.