|— City —|
Location in Butte County and the state of Idaho
|- Total||0.9 sq mi (2.3 km2)|
|- Land||0.9 sq mi (2.3 km2)|
|- Water||0.0 sq mi (0.0 km2)|
|Elevation||5,325 ft (1,623 m)|
|- Density||1,163.9/sq mi (449.4/km2)|
|Time zone||Mountain (MST) (UTC-7)|
|- Summer (DST)||MDT (UTC-6)|
|GNIS feature ID||0396049|
Craters of the Moon National Monument is located along U.S. Route 20, southwest of the city. The Idaho National Laboratory (INL) is located east of Arco. Arco is located along the Big Lost River and is a gateway to the Lost River Valley.
In 1901, the town, then known as Root Hog, moved its borders to place the town at the intersection of two stagecoach routes that crossed Idaho. The town leaders applied to the U.S. Post Office for the town name of "Junction."
The Postmaster General thought the name too common and suggested that the place be named Arco for Georg von Arco (1869-1940) of Germany who was visiting Washington, D.C. at the time. Georg von Arco was an inventor and a pioneer in the field of radio transmission and would become the lead engineer of Telefunken, a German company founded in 1903 that produced radio vacuum tubes.
Arco was the first community in the world ever to be lit by electricity generated by nuclear power. This occurred on July 17, 1955, powered by a reactor (see BORAX experiments) at the nearby "National Reactor Testing Station" (NRTS), which is now the Idaho National Laboratory. NRTS made further history on January 3, 1961, when the SL-1 reactor melted down, causing three deaths. It was the world's first (and the U.S.' only) fatal reactor accident.
The town's economic base is primarily derived from the Idaho National Laboratory (formerly the Idaho National Engineering Laboratory or INEL), agricultural products, and recreation in the Lost River Valley.
According to the U.S. Census Bureau, the city has a total area of 0.9 sq mi (2.3 km2), all of it land.
In town, the most striking physical feature is Number Hill, a rocky hill with numbers painted all over it. Butte County High School has a tradition of each class since 1920 painting its graduation year on the face of hill.
As of the census of 2000, there were 1,026 people, 427 households, and 269 families residing in the city. The population density was 1,163.9 people per square mile (450.2/km²). There were 505 housing units at an average density of 572.9/sq mi (221.6/km²). The racial makeup of the city was 95.13% White, 0.49% African American, 1.36% Native American, 1.75% from other races, and 1.27% from two or more races. Hispanic or Latino of any race were 3.61% of the population.
There were 427 households out of which 29.3% had children under the age of 18 living with them, 48.2% were married couples living together, 11.9% had a female householder with no husband present, and 37.0% were non-families. 34.0% of all households were made up of individuals and 15.2% had someone living alone who was 65 years of age or older. The average household size was 2.35 and the average family size was 3.04.
In the city the population was spread out with 27.9% under the age of 18, 6.8% from 18 to 24, 22.4% from 25 to 44, 25.8% from 45 to 64, and 17.1% who were 65 years of age or older. The median age was 40 years. For every 100 females there were 91.8 males. For every 100 females age 18 and over, there were 90.7 males.
The median income for a household in the city was $27,993, and the median income for a family was $34,688. Males had a median income of $34,688 versus $17,386 for females. The per capita income for the city was $14,744. About 19.6% of families and 22.6% of the population were below the poverty line, including 33.8% of those under age 18 and 15.8% of those age 65 or over.