Los Alamos County (English: "The Poplars" or "Cottonwoods"; ) is a county in the U.S. state of New Mexico. As of the 2020 census, the population was 19,419. The smallest county by area in the state, Los Alamos County was formerly administered exclusively by the U.S. federal government during the Manhattan Project, but it now has equal status to New Mexico's other counties. The county has two census-designated places: Los Alamos and White Rock.
Los Alamos County comprises the Los Alamos Micropolitan Statistical Area, which is also included in the Albuquerque–Santa Fe–Las Vegas combined statistical area.
The county is home to the Los Alamos National Laboratory. Los Alamos County is noted for having the lowest level of child poverty of any county in the United States.
Geography
According to the U.S. Census Bureau, the county has a total area of , of which is land and (0.08%) is water. It is the smallest county by area in New Mexico. There is no significant open water in the county. The county's highest point is located along its northern border, near the summit of Caballo Mountain, at above sea level.
Adjacent counties
Rio Arriba County – northeast
Santa Fe County – east
Sandoval County – south, west, north (and the Sandoval exclave to the east)
Pueblos with adjacent territories
Santa Clara Pueblo – northeast
San Ildefonso Pueblo – east
National protected areas
Bandelier National Monument (part) Santa Fe National Forest (part)
Demographics
2000 census
As of the 2000 census, there were 18,343 people, 7,497 households, and 5,337 families living in the county. The population density was . There were 7,937 housing units at an average density of . The racial makeup of the county was 90.3% White, 0.4% Black or African American, 0.6% Native American, 3.8% Asian, <0.1% Pacific Islander, 2.7% from other races, and 2.3% from two or more races. 11.8% of the population were Hispanic or Latino of any race.
There were 7,497 households, out of which 33.5% had children under the age of 18 living with them, 62.7% were married couples living together, 5.7% had a female householder with no husband present, and 28.8% were non-families. 24.9% of all households were made up of individuals, and 6.7% had someone living alone who was 65 years of age or older. The average household size was 2.43 and the average family size was 2.92.
In the county, the population was spread out, with 25.8% under the age of 18, 4.4% from 18 to 24, 27.7% from 25 to 44, 30.0% from 45 to 64, and 12.1% who were 65 years of age or older. The median age was 41 years. For every 100 females there were 101.40 males. For every 100 females age 18 and over, there were 99.70 males.
The median income for a household in the county was $78,993, and the median income for a family was $90,032. Males had a median income of $70,063 versus $40,246 for females. The per capita income for the county was $34,646. 2.9% of the population and 1.9% of families were below the poverty line. 1.8% of those under the age of 18 and 4.7% of those 65 and older were living below the poverty line.
2010 census
As of the 2010 census, there were 17,950 people, 7,663 households, and 5,199 families living in the county. The population density was . There were 8,354 housing units at an average density of . The racial makeup of the county was 87.8% white, 6.0% Asian, 0.8% American Indian, 0.6% black or African American, 0.1% Pacific islander, 2.2% from other races, and 2.6% from two or more races. Those of Hispanic or Latino origin made up 14.7% of the population. In terms of ancestry, 18.9% were German, 16.5% were English, 13.2% were Irish, and 6.5% were American.
Of the 7,663 households, 31.3% had children under the age of 18 living with them, 58.1% were married couples living together, 6.4% had a female householder with no husband present, 32.2% were non-families, and 28.5% of all households were made up of individuals. The average household size was 2.33 and the average family size was 2.86. The median age was 44.3 years.
The median income for a household in the county was $103,643 and the median income for a family was $118,993. Males had a median income of $93,040 versus $51,753 for females. The per capita income for the county was $49,474. About 1.4% of families and 2.4% of the population were below the poverty line, including 1.8% of those under age 18 and 2.4% of those age 65 or over.