Millions of years ago, the Mississippi River was vastly different from today—at certain points it was up to five miles wide, and whales from the Gulf of Mexico could swim far inland through its waters. Remarkably, fossils of these ancient whales have even been discovered in Michigan. The Mississippi River was once far larger than it is today. Following the last Ice Age, massive amounts of glacial meltwater poured southward, creating an enormous river system with channels and floodplains that stretched for miles. In some places, the Mississippi basin was nearly five miles wide. These waterways were connected to the Gulf of Mexico, allowing marine animals such as whales to travel surprisingly far inland. Although the Mississippi remained a freshwater river, some ancient whales—much like certain species today—could tolerate freshwater for extended periods while moving through connected river systems. Whale remains have been discovered hundreds of miles from the ocean, including in Michigan. Other inland whale fossils date to even earlier periods when shallow seas covered large portions of North America. Over thousands of years, retreating glaciers, changing sea levels, and shifting river channels dramatically reshaped the landscape. What is now a single river was once part of an immense freshwater network connected to the Gulf, carrying enough water to help transform an entire continent.(Historic Vids)