Continental ice sheets, a type of glacier, advanced and retreated throughout the Ice Age. At various times this ice extended down into the northern regions of the United States. New York, New England, and the northern Midwest retain evidence from these fairly recent glaciers.

The end of the Pleistocene is marked by the extinction of horses and many other large mammals in North America. Some of the animals that died out in North America survived in other regions. For example, llamas survived in South America and tapirs survived in Asia and South America. Two elephant genera survive in the Old World, in Africa and India, but all the mammoths and mastodons became extinct.