Monrovia is a city located in the foothills of the San Gabriel Mountains in the San Gabriel Valley of Los Angeles County, California, United States. The population was 36,929 at the 2000 census.

Monrovia is located at 34°8′39″N 118°0′7″W / 34.14417°N 118.00194°W / 34.14417; -118.00194 (34.144156, -118.001848).

According to the United States Census Bureau, the city has a total area of 35.8 square kilometers (13.8 sq mi). 35.6 km² (13.8 mi²) of it is land and 0.2 km² (0.1 mi²) of it (0.51%) is water.

As of the census of 2000, there were 36,929 people, 13,502 households, and 9,086 families residing in the city. The population density was 1,037.0/km² (2,686.5/mi²). There were 13,957 housing units at an average density of 391.9/km² (1,015.3/mi²). The racial makeup of the city was 62.92% White, 8.67% African American, 0.87% Native American, 7.02% Asian, 0.13% Pacific Islander, 15.61% from other races, and 4.77% from two or more races. Hispanic or Latino of any race were 35.24% of the population.

There were 13,502 households out of which 35.4% had children under the age of 18 living with them, 46.4% were married couples living together, 15.4% had a female householder with no husband present, and 32.7% were non-families. 26.0% of all households were made up of individuals and 8.8% had someone living alone who was 65 years of age or older. The average household size was 2.71 and the average family size was 3.29.

In the city the population was spread out with 27.4% under the age of 18, 8.0% from 18 to 24, 34.0% from 25 to 44, 20.2% from 45 to 64, and 10.4% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 92.2 males. For every 100 females age 18 and over, there were 87.6 males.

The median income for a household in the city was $45,375, and the median income for a family was $49,703. Males had a median income of $41,039 versus $32,259 for females. The per capita income for the city was $21,686. About 9.7% of families and 13.1% of the population were below the poverty line, including 18.3% of those under age 18 and 9.7% of those age 65 or over.

In the state legislature Monrovia is located in the 29th Senate District, represented by Republican Bob Huff, and in the 44th and 59th Assembly Districts, represented by Democrat Anthony J. Portantino and Republican Anthony Adams respectively. Federally, Monrovia is located in California's 26th congressional district, which has a Cook PVI of R +4 and is represented by Republican David Dreier.

The Los Angeles County Department of Health Services operates the Monrovia Health Center in Monrovia.

Monrovia is the fourth oldest general law city in Los Angeles County and the L.A. Basin (after Los Angeles, Santa Monica, and Pasadena). Incorporated in 1887, Monrovia has grown from a sparse community of orange ranches to a residential community of 37,000. People traveling between Los Angeles and San Bernardino traveled "via Monroe's Ranch," hence the name.[citation needed]