The Judith River Formation is a late Cretaceous geological formation that was primarily deposited in North Central Montana 80 to 75 million years ago about the same time as the Two Medicine Formation, See Map -        Large meandering rivers flowing into the Intercontinental Cretaceous Seaway deposited the Formation. Much of the area was very flat, with swamps and bogs, much like today's southern Louisiana. Dinosaurs included Tyrannosaurs, the duck-bills hadrosaur Brachyl