The city once shared three different postal ZIP codes with Long Beach, but in July 2002, the City of Signal Hill received its own ZIP code, 90755. It is in the 562 area code.
The 2005 population according to the State of California's Department of Finance is 10,951 [1].
As of the census of 2000, there were 9,333 people, 3,621 households, and 2,096 families residing in the city. The population density was 1,615.9/km² (4,182.0/mi²). There were 3,797 housing units at an average density of 657.4/km² (1,701.4/mi²). The racial makeup of the city was 45.48% White, 12.99% African American, 0.59% Native American, 16.49% Asian, 2.08% Pacific Islander, 16.18% from other races, and 6.19% from two or more races. Hispanic or Latino of any race were 29.00% of the population.
There were 3,621 households out of which 31.0% had children under the age of 18 living with them, 36.8% were married couples living together, 14.5% had a female householder with no husband present, and 42.1% were non-families. 30.6% of all households were made up of individuals and 5.2% had someone living alone who was 65 years of age or older. The average household size was 2.56 and the average family size was 3.34.
In the city the population was spread out with 26.4% under the age of 18, 9.1% from 18 to 24, 35.3% from 25 to 44, 22.0% from 45 to 64, and 7.2% who were 65 years of age or older. The median age was 33 years. For every 100 females there were 97.1 males. For every 100 females age 18 and over, there were 96.1 males.
The median income for a household in the city was $48,938, and the median income for a family was $46,439. Males had a median income of $41,487 versus $36,460 for females. The per capita income for the city was $24,399. About 13.6% of families and 17.2% of the population were below the poverty line, including 31.1% of those under age 18 and 3.9% of those age 65 or over.