Geophysical Lake Michigan
- the second largest
- the only Great Lake entirely within the United States
- variable climate, population density and development
- northern part: colder, less developed, sparsely populated
- southern basin: more temperate, among the most urbanized areas in the Great Lakes system.
- Milwaukee and Chicago metropolitan areas have about 8 million people, 20% of the total population of the Great Lakes basin
- Green Bay has one of the most productive Great Lakes fisheries but receives the wastes from the world's largest concentration of pulp and paper mills