Lighthouses in the Great Lakes were built to keep ships carrying grain, timber, fur and minerals off the bottom of the lakes. Between 1878 and 1898, 6,000 Great Lakes ships wrecked. Ship owners who lost a lot of time and money lobbied the federal government to install more navigational aids. By 1925 there were 433 lighthouses, 10 lightships and 120 fog signals.
"Focus on Great Lakes Water Quality (ISSN 0711-0855): vol.9 iss.4,"
Focus on International Joint Commission Activities: Vol. 9
, Article 1.
Available at: http://scholar.uwindsor.ca/ijcfocus/vol9/iss4/1