Members of Arizona's congressional delegation have introduced legislation to expand the boundaries of Casa Grande Ruins National Monument.
The monument in Coolidge includes one of the largest prehistoric structures ever built in North America. The National Park Service says the purpose of the "Great House" remains a mystery.
It is believed to have been built by the ancient Sonoran Desert people who practiced wide-scale irrigation farming and had extensive trade connections over 1,000 years.
Legislation introduced Tuesday by Democratic Reps. Ann Kirkpatrick, Ed Pastor and Raul Grijalva, and Republican Rep. Paul Gosar would add 10 acres to the monument. That includes Hohokam villages associated with the "Great House," a second village area and a segment of a prehistoric canal.
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