Eagle is a city in Ada County, Idaho, United States. The population was 19,908 at the 2010 census.
According to the United States Census Bureau, the city has a total area of 29.40 square miles (76.15 km2), of which 28.92 square miles (74.90 km2) is land and 0.48 square miles (1.24 km2) is water.
This region experiences warm to hot, dry summers, and cold, dry winters, with summer high temperatures averaging 85 °F and winter low temperatures averaging 25.6 °F. According to the Köppen climate classification system, Eagle has a warm-summer Mediterranean climate, abbreviated "Csb" on climate maps.
At the 2010 census there were 19,908 people, 7,069 households, and 5,585 families living in the city. The population density was 688.4 inhabitants per square mile (265.8/km2). There were 7,570 housing units at an average density of 261.8 per square mile (101.1/km2). The racial makeup of the city was 94.4% White, 0.3% African American, 0.5% Native American, 1.6% Asian, 0.1% Pacific Islander, 1.0% from other races, and 2.0% from two or more races. Hispanic or Latino of any race were 4.7%.
Of the 7,069 households 41.5% had children under the age of 18 living with them, 67.9% were married couples living together, 7.9% had a female householder with no husband present, 3.2% had a male householder with no wife present, and 21.0% were non-families. 17.7% of households were one person and 8.5% were one person aged 65 or older. The average household size was 2.82 and the average family size was 3.20.
The median age was 40.6 years.