Chaco Culture National Historical Park [NM]
"Chaco Culture National Historical Park preserves one of America's most significant and fascinating cultural and historic areas. Chaco Canyon was a major center of ancestral Puebloan culture between AD 850 and 1250. It was a hub of ceremony, trade, and administration for the prehistoric Four Corners area - unlike anything before or since."
Self-guided hikes and bus/car tours are available. Group camping is also an option for school groups. Curriculum materials can be downloaded and are suggested for use before your visit.