Henry Schoolcraft discovered a lake in what county?
Schoolcraft River:  The river is named after Henry Schoolcraft, who mapped the region and discovered nearby Lake Itasca as the source of the Mississippi in 1831. Lake Itasca:  It is notable for being the headwaters of the Mississippi River, and is located in southeastern Clearwater County, in the Headwaters area of north central Minnesota.
Clearwater County