Great Lakes tectonic zone southern Ontario. Several earthquakes have been documented in Minnesota in the last 120 years, with at least six in the GLTZ. The epicenters show a clear relationship to tectonic features of the state; four epicenters lie along the Great Lakes tectonic zone. Depths are estimated at . The best-documented event occurred on July 9, 1975, near Morris, Minnesota, with a magnitude of 4.6, and a felt area of covering parts of four states. Wisconsin has had no earthquakes along the GLTZ, Michigan's Upper Peninsula has had four earthquakes in the vicinity of the GLTZ – Negaunee, Newberry and two in
The Great Lakes Group was the first president. The company began full operation on the Great Lakes (except Lake Ontario and the St. Lawrence River) in 1900, starting its first navigating season with over 150 tugboats. The Company grew rapidly, so much so that in 1913 it was charged with operating a monopoly. Frequent labor unrest during World War II resulted in the U.S. government assuming control of the Company in 1945-46. During the 1950s and 1960s the company installed innovative communication equipment. Business began to decline in the 1960s when the decline of the steel industry and the introduction of new types of