Colton is the site of Colton Crossing, one of the busiest at-grade railroad crossings in the United States. The main transcontinental trunk lines of Union Pacific and Burlington Northern Santa Fe cross at this point. As traffic on each line has soared since the mid-1990s, fueled largely by the vast increase in imports passing through the ports of Los Angeles and Long Beach, the primitive crossing has become a serious bottleneck. The crossing was installed in August 1882 by the California Southern Railroad to cross the Southern Pacific Railroad's tracks while building northward from San Diego.
As of the censusGR2 of 2000, there were 47,662 people, 14,520 households, and 10,904 families residing in the city. The population density was 1,217.9/km² (3,154.3/mi²). There were 15,680 housing units at an average density of 400.7/km² (1,037.7/mi²). The racial makeup of the city was 42.68% White, 11.01% African American, 1.26% Native American, 5.29% Asian, 0.23% Pacific Islander, 34.46% from other races, and 5.08% from two or more races. Hispanic or Latino of any race were 60.71% of the population.
There were 14,520 households out of which 46.5% had children under the age of 18 living with them, 48.3% were married couples living together, 19.5% had a female householder with no husband present, and 24.9% were non-families. 19.4% of all households were made up of individuals and 4.6% had someone living alone who was 65 years of age or older. The average household size was 3.26 and the average family size was 3.76.
In the city the population was spread out with 34.9% under the age of 18, 11.9% from 18 to 24, 31.5% from 25 to 44, 15.2% from 45 to 64, and 6.4% who were 65 years of age or older. The median age was 27 years. For every 100 females there were 97.2 males. For every 100 females age 18 and over, there were 93.8 males.
The median income for a household in the city was $35,777, and the median income for a family was $37,911. Males had a median income of $32,152 versus $25,118 for females. The per capita income for the city was $13,460. About 18.2% of families and 19.6% of the population were below the poverty line, including 25.2% of those under age 18 and 10.9% of those age 65 or over.