Casa Grande Ruins National Monument, Archaeological site in Coolidge, Arizona.

Casa Grande is the largest structure at this monument in Coolidge, Arizona: a four-story caliche building about 60 feet on each side, with outer rooms three stories high surrounding a four-story inner core. Its walls are aligned to the cardinal directions, and horizontal cracks mark the breaks between adobe courses. The ruin stands under a 1932 shelter designed by Frederick Law Olmsted Jr.

The Hohokam built this settlement between 1300 and 1450 as part of a larger network of farms that eventually abandoned the area. The site became a protected monument in 1892, marking one of the first times the nation preserved a prehistoric location.

The name Casa Grande is Spanish for "big house"; the O'odham call it Siwañ Waʼa Ki:. When Padre Eusebio Kino reached the site in 1694, the nearby Pima told him their ancestors, the Ho-ho-kahm, had lived there, a name meaning "all gone" in their language. Visitors can see 19th-century graffiti scratched into the walls, now illegal.

The site sits in the Sonora Desert and is open year-round, with a covered steel shelter protecting the main structure. The ground is flat and easy to walk on, but bring water and sun protection as shade is limited throughout the grounds.

The protective roof over the Great House was designed by Frederick Law Olmsted Jr., son of the Central Park landscape architect, and built in 1932; it replaced a wooden shelter from 1903. In the early 21st century a pair of great horned owls nested in its rafters. Visitors may only view the structure from outside.