In 1971, researchers began mapping the archaeological sites in Chaco Canyon. Today, it is believed that there are more than 3,000, and that only about 1 percent has been excavated. In the early 1100's a fifty year drought had set in, making life very difficult. At this time new construction stopped. The people that inhabited Chaco did not just vanish. Instead, they moved on to areas that became more hospitable. Many are believed to have moved to the area where today we find the Aztec Ruins National Park. This site is on the Animas River. Soon other regional centers sprung up. However, when another major 25 year drought arrived in 1275, it is believed that every single person left the area for good. Eventually, they evolved into the Hopi, Navajo, Pueblo, Toltec, and very possibly the Aztec cultures.