Prior to the uplift of the Rocky Mountains that one sees today, there was an earlier mountain range in Colorado called the Ancestral Rocky Mountains. As one drives along Interstate 70 across Vail Pass and towards Vail, there are red rocks along the highway that transition to gray rocks as one approaches Vail. These rocks are sandstones eroded off the rising Ancestral Rocky Mountains. The discussion will cover how these mountains were formed, the basins that formed adjacent to the mountains, the sediments that filled the basins and the subsequent history of the basins.