Before the Seaway was built, there was no way for boats and ships to get around the rapids and dams on the Saint Lawrence River. Big ships could not pass Niagara Falls, the waterfalls on the Niagara River between Lake Ontario and Lake Erie. In the early 20th century, the governments of both Canada and the U.S. saw that the cities near the Great Lakes could grow and become an important part of the economy of both countries. There were people in both countries who did not want the Seaway to be built, but the project went ahead.