The Great Lakes are struggling with a great deal of pollution from agricultural chemical run-off, commercial shipping and tourist use. Many smaller lakes in the region are popular and less polluted. Only the polar ice caps contain more fresh water. In the northern areas, the lakes are cool or cold until August or September.
Lake Superior is the largest, deepest and coldest.
It is also one of the least polluted among the lakes. Lake Michigan is the second largest and is the only lake entirely in the United States. Colder and sparsely developed to the north, Michigan is highly developed in the southern area with Milwaukee and Chicago. Lake Huron is the third largest and offers a great deal of fishing. Lake Erie, the second smallest, is the shallowest and the warmest of the lakes.