Rocklin is a city in Placer County, California located in the metropolitan area of Sacramento. It shares borders with Roseville, Loomis, and Lincoln. As of the 2010 census, the city's population was 56,974.

Although European-Americans were probably fishing and harvesting game in the Rocklin area in the late 18th and early 19th centuries, major European-American settlement started in the early 1850s as fortune hunters sluiced for gold in Secret Ravine, an area of oaks and dredger tailings that can be found today southeast of Interstate 80 between Roseville and Loomis.

The 2010 United States Census reported that Rocklin had a population of 56,974. The population density was 2,907.7 people per square mile (1,122.7/km²). The racial makeup of Rocklin was 47,047 (82.6%) White, 858 (1.5%) African American, 410 (0.7%) Native American, 4,105 (7.2%) Asian, 150 (0.3%) Pacific Islander, 1,538 (2.7%) from other races, and 2,866 (5.0%) from two or more races. Hispanic or Latino of any race were 6,555 persons (11.5%).

The Census reported that 56,337 people (98.9% of the population) lived in households, 456 (0.8%) lived in non-institutionalized group quarters, and 181 (0.3%) were institutionalized.

There were 20,800 households, out of which 8,424 (40.5%) had children under the age of 18 living in them, 11,974 (57.6%) were opposite-sex married couples living together, 2,191 (10.5%) had a female householder with no husband present, 895 (4.3%) had a male householder with no wife present. There were 1,035 (5.0%) unmarried opposite-sex partnerships, and 124 (0.6%) same-sex married couples or partnerships. 4,403 households (21.2%) were made up of individuals and 1,652 (7.9%) had someone living alone who was 65 years of age or older. The average household size was 2.71. There were 15,060 families (72.4% of all households); the average family size was 3.18.

The population was spread out with 15,613 people (27.4%) under the age of 18, 5,306 people (9.3%) aged 18 to 24, 15,159 people (26.6%) aged 25 to 44, 14,668 people (25.7%) aged 45 to 64, and 6,228 people (10.9%) who were 65 years of age or older. The median age was 36.7 years. For every 100 females there were 94.0 males. For every 100 females age 18 and over, there were 90.4 males.

There were 22,010 housing units at an average density of 1,123.3 per square mile (433.7/km²), of which 13,797 (66.3%) were owner-occupied, and 7,003 (33.7%) were occupied by renters. The homeowner vacancy rate was 2.5%; the rental vacancy rate was 7.3%. 39,295 people (69.0% of the population) lived in owner-occupied housing units and 17,042 people (29.9%) lived in rental housing units.

2000

As of the census of 2000, there were 36,330 people, 13,258 households, and 10,009 families residing in the city. The population density was 2,246.2 people per square mile (867.5/km²). There were 14,421 housing units at an average density of 891.6 per square mile (344.3/km²). The racial makeup of the city was 88.32% White, 0.91% African American, 0.80% Native American, 4.16% Asian, 0.19% Pacific Islander, 1.93% from other races, and 3.69% from two or more races. Hispanic or Latino of any race were 7.91% of the population. 16.8% were of German, 11.8% English, 10.6% Irish, 8.1% Italian and 6.5% American ancestry according to Census 2000.

There were 13,258 households out of which 42.6% had children under the age of 18 living with them, 62.3% were married couples living together, 9.4% had a female householder with no husband present, and 24.5% were non-families. 18.7% of all households were made up of individuals and 6.3% had someone living alone who was 65 years of age or older. The average household size was 2.74 and the average family size was 3.15.

In the city the population was spread out with 30.0% under the age of 18, 7.0% from 18 to 24, 33.7% from 25 to 44, 20.8% from 45 to 64, and 8.6% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 95.6 males. For every 100 females age 18 and over, there were 92.6 males.

The median income for a household in the city was $84,508, according to the City of Rocklin website. Males had a median income of $54,426 versus $35,920 for females. The per capita income for the city was $26,910. About 3.1% of families and 4.5% of the population were below the poverty line, including 4.3% of those under age 18 and 3.5% of those age 65 or over.