Chicago is located in the midwest of the United States, belonging to Illinois, with Lake Michigan in the east. The origin of the lake: it was originally a valley structure, surrounded by terminal moraine, and it was originally a huge lake basin because of the accumulation of a large number of sediments and stones carried by Quaternary glaciers. When the weather gets warmer, glaciers melt, water accumulates in rocks and eventually becomes a lake. The Great Lakes are the largest freshwater lakes in the world, with high altitude in the west and low altitude in the east. Because the soil near the lake is mostly moraine soil, which is beneficial to agricultural cultivation and suitable for planting pasture, it has become the main supplier of fresh milk in metropolitan areas of North America.