Coolidge is a city in Pinal County, Arizona, United States. According to the 2010 census, the city's population is 11,825.
Coolidge is home of the Casa Grande Ruins National Monument. The monument was the first historic site to receive protected status by the United States Government in 1892. Coolidge is also home to both Central Arizona College and the Central Arizona Valley Institute of Technology.
The area containing what is now the City of Coolidge was occupied by indigenous ancient Sonoran Desert people who built a massive compound consisting many of caliche structures and remained in the area for over 1,000 years before abandoning it approximately 560 years ago for unknown reasons. The only remaining and preserved structure from this compound is the Casa Grande Ruins National Monument.
The modern history of the city is centered around agriculture, particularly cotton. Coolidge was founded in 1925 when R.J. Jones laid out an 80 acres (32 ha) site during the construction of the Coolidge Dam on the nearby Gila River, which was completed in 1930. Both the dam and the townsite were named for Calvin Coolidge, the 30th President of the United States. The dam made the sandy soil native to the area into very rich farmland, and soon vast expanses of desert were plowed and acres of cotton were planted.