Lake Itasca (Wikipedia) Lake Itasca (/aɪˈtæskə/ eye-TASS-kə) is a small glacial lake, approximately 1.8 square miles (4.7 km2; 1,200 acres) in area. Located in southeastern Clearwater County, in the Headwaters area of north central Minnesota, it is notable for being the headwater of the Mississippi River. The lake is in Itasca State Park. It has an average depth of 20 to 35 feet (6.1 to 10.7 m) and is 1,475 feet (450 m) above sea level.