Official Site: https://www.nps.gov/chcu/index.htm
Wikipedia: https://en.wikipedia.org/wiki/Chaco_Culture_National_Historical_Park
Facebook: https://www.facebook.com/nps.chcu
Twitter: https://twitter.com/chacoculturenhp
From LiveScience:
President Theodore Roosevelt recognized these alluring ruins in 1907 when he designated Chaco Canyon a national monument. The ruins were placed on the National Register of Historic Places in 1966.
In 1980, the boundary of the national monument was enlarged by 20 square miles (52 square kilometers) and the monument became the Chaco Culture National Historical Park.
Associated Press