The St. Lawrence Seaway, often called one of North America’s greatest infrastructure achievements, was a joint venture between Canada and the United States completed in 1959. The waterway connects the Great Lakes to the Atlantic Ocean, allowing large ships to bypass natural obstacles like rapids and waterfalls, including Niagara Falls. Despite its shared benefits, Canada paid for about 75% of the project, largely because political opposition in the U.S. delayed American funding. Many U.S. interest groups, such as railroads and port cities, feared the canal would hurt their businesses, leaving Canada to shoulder the bulk of the financial burden to push the project forward. The Seaway includes 15 locks and stretches over 2,300 miles, revolutionizing trade by creating a direct maritime route to the industrial heartland of both countries. Today, the St. Lawrence Seaway is a critical artery for global trade, cementing its role as one of the most significant engineering marvels of the 20th century.