The Western Interior Seaway[1] was a huge inland sea. It split North America into two halves for most of the mid- and late-CretaceousPeriod. It was up to 2,500 feet (760 m) deep, 600 miles (970 km) wide and over 2,000 miles (3,200 km) long.
↑also called the Cretaceous Seaway, the Niobraran Sea, and the North American Inland Sea