The Agua Fria National Monument contains one of the most significant systems of late prehistoric sites in the American Southwest. Its ancient ruins offer insights into the lives of those who long ago inhabited this part of the desert southwest. Between A.D. 1250 and 1450, the area's pueblo communities were populated by up to several thousand people. At least 450 prehistoric sites are known to exist within the monument area and there are likely many more.

There are at least four major settlements within the area, including Pueblo La Plata, Pueblo Pato, the Baby Canyon Ruin group, and the Lousy Canyon group. These consist of clusters of stone-masonry pueblos, some containing at least one hundred rooms. In addition, there are many intact petroglyphs, as well as remnants of prehistoric agricultural features. The monument also contains historic sites representing early Anglo-American history through the nineteenth century, including remnants of Basque sheep camps, historic mining features, and military activities.

In the last few decades, the area has received increased recognition as an outstanding archaeological resource. The majority of public land in the area was acquired around 1990 from the State of Arizona and in two private exchanges. The area contains most of a National Register of Historic Places District. Originally designated in 1975, the District was expanded in 1996 to encompass approximately 50,000 acres managed by the BLM and the Tonto National Forest. It is one of the largest prehistoric districts listed on the National Register of Historic Places.