Lake Powell is a reservoir on the Colorado River. It is mainly in southeastern Utah, with a small part in northeastern Arizona in the United States. About long, it is made by the Glen Canyon Dam, built in Glen Canyon in the 1960s. The lake is a popular area for boating and fishing, with over 2 million visitors each year; but it has flooded many important natural and archaeological sites. Other than the Colorado River, the Escalante River and San Juan River also flow into the reservoir.