Crestline is located at 34°14′33″N 117°17′24″W.
According to the United States Census Bureau, Crestline has a total area of 14.0 square miles (36 km2). 13.8 square miles (36 km2) of it is land and 0.1 square miles (0.26 km2) of it (1.00%) is water.
Crestline is located within the San Bernardino National Forest; Lake Gregory is located in the center of Crestline.
According to the Köppen Climate Classification system, Crestline has a warm-summer Mediterranean climate, abbreviated Csb on climate maps.
The 2010 United States Census reported that Crestline had a population of 10,770. The population density was 770.4 people per square mile (297.5/km²). The racial makeup of Crestline was 9,289 (86.2%) White (77.0% Non-Hispanic White), 107 (1.0%) African American, 135 (1.3%) Native American, 96 (0.9%) Asian, 20 (0.2%) Pacific Islander, 526 (4.9%) from other races, and 597 (5.5%) from two or more races. Hispanic or Latino of any race were 1,775 persons (16.5%).
The Census reported that 10,723 people (99.6% of the population) lived in households, 39 (0.4%) lived in non-institutionalized group quarters, and 8 (0.1%) were institutionalized.
There were 4,360 households, out of which 1,286 (29.5%) had children under the age of 18 living in them, 2,108 (48.3%) were opposite-sex married couples living together, 451 (10.3%) had a female householder with no husband present, 247 (5.7%) had a male householder with no wife present. There were 309 (7.1%) unmarried opposite-sex partnerships, and 57 (1.3%) Homosexual. 1,190 households (27.3%) were made up of individuals and 362 (8.3%) had someone living alone who was 65 years of age or older. The average household size was 2.46. There were 2,806 families (64.4% of all households); the average family size was 2.97.
The population was spread out with 2,375 people (22.1%) under the age of 18, 875 people (8.1%) aged 18 to 24, 2,383 people (22.1%) aged 25 to 44, 3,838 people (35.6%) aged 45 to 64, and 1,299 people (12.1%) who were 65 years of age or older. The median age was 43.3 years. For every 100 females there were 103.2 males. For every 100 females age 18 and over, there were 103.5 males.
There were 7,333 housing units at an average density of 524.6 per square mile (202.5/km²), of which 3,123 (71.6%) were owner-occupied, and 1,237 (28.4%) were occupied by renters. The homeowner vacancy rate was 6.7%; the rental vacancy rate was 13.8%. 7,463 people (69.3% of the population) lived in owner-occupied housing units and 3,260 people (30.3%) lived in rental housing units.
According to the 2010 United States Census, Crestline had a median household income of $50,079, with 16.8% of the population living below the federal poverty line.
As of the census of 2000, there were 10,218 people, 4,000 households, and 2,767 families residing in the CDP. The population density was 940.4 inhabitants per square mile (362.9/km²). There were 6,695 housing units at an average density of 616.2 per square mile (237.8/km²). The racial makeup of the CDP was 88.0% White, 0.8% African American, 1.1% Native American, 0.6% Asian, 0.2% Pacific Islander, 5.0% from other races, and 4.3% from two or more races. Hispanic or Latino of any race were 10.5% of the population.
There were 4,000 households out of which 33.4% had children under the age of 18 living with them, 53.0% were married couples living together, 10.6% had a female householder with no husband present, and 30.8% were non-families. 24.7% of all households were made up of individuals and 6.6% had someone living alone who was 65 years of age or older. The average household size was 2.6 and the average family size was 3.0.
In the CDP, the population was spread out with 27.8% under the age of 18, 6.3% from 18 to 24, 27.7% from 25 to 44, 29.1% from 45 to 64, and 9.1% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 100.6 males. For every 100 females age 18 and over, there were 97.0 males.
The median income for a household in the CDP was $44,257, and the median income for a family was $51,655. Males had a median income of $48,772 versus $28,750 for females. The per capita income for the CDP was $20,987. About 6.6% of families and 8.9% of the population were below the poverty line, including 10.7% of those under age 18 and 4.8% of those age 65 or over.
In the California State Legislature, Crestline is in the 23rd Senate District, represented by Republican Mike Morrell, and in the 33rd Assembly District, represented by Republican Jay Obernolte.
In the United States House of Representatives, Crestline is in California's 8th congressional district, represented by Republican Paul Cook.
The Crestline community is served by the Rim of the World Unified School District. It includes four (K-5) elementary schools (Valley of Enchantment, Charles Hoffman, Grandview, Lake Arrowhead), one (6-8) intermediate school (Mary P. Henick), two high schools (Mountain, Rim Of The World Senior), and one alternative high school (Lake Gregory Education Center, formerly Lake Gregory Elementary. The previous alternative high school was Mountain High, formerly the Mary Tone Elementary Building).