Benton County is part of the Fayetteville–Springdale–Rogers, AR-MO Metropolitan Statistical Area.
As of the census of 2000, there were 153,406 people, 58,212 households, and 43,484 families residing in the county. The population density was 181 people per square mile (70/km²). There were 64,281 housing units at an average density of 76 per square mile (29/km²). The racial makeup of the county was 90.87% White, 0.41% Black or African American, 1.65% Native American, 1.09% Asian, 0.08% Pacific Islander, 4.08% from other races, and 1.82% from two or more races. 8.78% of the population were Hispanic or Latino of any race.
As of 2005 Benton County's population was 81.7% non-Hispanic white, while the percentage of Latinos grew by 60 percent in the time period. Latinos are attracted to the growth of light industrial jobs, home construction and service sector in the county. 1.1% of the population was African-American (perhaps the lowest in all of Arkansas); 1.6% was Native American (the historical presence of the Cherokee Indians live in close proximity to Oklahoma); 1.7% was Asian (there was a large influx of Filipinos, Vietnamese and South Asian immigrants arrived in recent decades) and 0.2% of the population was Pacific Islander. 1.6% reported two or more races, usually not black-white due to a minuscule African-American population. And 12.8% was Latino, but the United States Hispanic Chamber of Commerce believed the official estimate is underreported and Latinos could well be 20 percent of the population.
There were 58,212 households out of which 34.40% had children under the age of 18 living with them, 63.00% were married couples living together, 8.20% had a female householder with no husband present, and 25.30% were non-families. 21.10% of all households were made up of individuals and 8.50% had someone living alone who was 65 years of age or older. The average household size was 2.60 and the average family size was 3.01.
In the county the population was spread out with 26.60% under the age of 18, 8.60% from 18 to 24, 29.40% from 25 to 44, 21.10% from 45 to 64, and 14.30% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 97.40 males. For every 100 females age 18 and over, there were 94.90 males.
The median income for a household in the county was $40,281, and the median income for a family was $45,235. Males had a median income of $30,327 versus $22,469 for females. The per capita income for the county was $19,377. About 7.30% of families and 10.10% of the population were below the poverty line, including 13.80% of those under age 18 and 7.30% of those age 65 or over.
The Northwest Arkansas Regional Airport is located near Highfill.
The Arkansas and Missouri Railroad parallels US Highways 62 and 71 in the county