Duluth, Minnesota four Catholic schools with coverage up to grades 6 or 8, two Protestant schools, two Montessori schools, and six other charter and private schools. Due to its proximity to the Great Lakes, Duluth is the location for the Large Lakes Observatory. The Large Lakes Observatory operates the largest university-owned research vessel in the Great Lakes, the R/V Blue Heron. Built in 1985 for fishing on the Grand Banks, the Blue Heron was purchased by the University of Minnesota in 1997, sailed from Portland, Maine, up the St. Lawrence Seaway to Duluth, and converted into a limnological research vessel during the
Proglacial lakes of Minnesota occupying parts of the Lake Superior basin. As its current outlet to the east was blocked by the Superior Lobe of the ice sheet, Lake Duluth drained through two outlets which crossed the present Laurentian Divide to the valley of the Saint Croix River and the Mississippi. One outlet was a route from the western part of the lake through the Nemadji River basin and down the present Moose and Kettle Rivers; the other was via the modern Bois Brule River to the Saint Croix. At its peak, Lake Duluth was 148 meters higher than Superior's present level. When the