Beloved in Wisconsin and the upper Midwest, and critical to the nation, the Great Lakes are only 3,000 years old in their current, widely recognized shapes, the “youngest major geological feature on the planet.” But the conditions that led to their formation began two million years before, with falling snow and the formation of glaciers. This informational picture book begins by detailing how the Great Lakes, which contain most of the freshwater in North America, formed. It then follows a drop of water as it moves from Lake Superior to Huron, to Michigan, to Erie, then over Niagara Falls, into Lake Ontario, down the St. Lawrence River and finally into the Atlantic Ocean. A final section looks at how humans have used the Great Lakes—first Native peoples, and then European settlers, who contributed vast amounts of pollution, before Indigenous activists led efforts to clean up the Lakes. A narrative deftly weaving science, history, and environmental activism is paired with illustrations depicting the lakes’ geologic and human history as well as their beauty.