Spanning over 750 miles across eastern North America, the Great Lakes are a chain of immense inland freshwater seas that have deeply shaped the environment, economies, and cultures of midcontinental regions in the United States and Canada. This expansive article explores the geographical significance and natural history of the Great Lakes system, tracing their origins from massive glaciers of the last Ice Age to modern day influences on regional climate, diverse ecosystems, and natural resource utilization. Delving into early Native American lifeways, European exploration and the colonial fur trade around the lakes, the piece also highlights the pivotal role of Great Lakes transportation networks and industry in accelerating settlement and urbanization across the Midwest and Ontario. More than a vital commercial crossroads, this vast watershed remains an iconic natural wonder at the heart of the North American continent.