Mesa Verde National Park's archaeological sites span over 700 years of Native American history. The renowned cliff dwellings, the height of the Puebloans' architecture, include more than 600 alcove sites. Many of these sites, such as Spruce Tree House, Square Tower House and Fire Temple, were built towards the end of the Ancestral Puebloan occupation of the Mesa. Each cliff dwelling was adapted to the topography of its alcove, making these hundreds of archaeological sites unique. While Mesa Verde's structures are centuries old, it remains an important place for American Indian communities today. Many of the sovereign Pueblo nations in New Mexico and Colorado can trace their ancestry back to this region. After Mesa Verde became known to researchers in 1874, collectors heavily pillaged the site which contained weaving, wickerwork, and ceramics of remarkable quality. However, in 1906 the site became protected under the Federal Antiquities Act, signed into law by Theodore Roosevelt, making it one of the world's best managed natural, biological and archaeological reserves.