The world’s longest undefended border is 3,000 miles (4828 km) long. It lies between Canada and the United States. Because they are the world’s largest trading partners, many opportunities are available for passage between the two countries. The Peace Bridge is located near the center of downtown Buffalo, New York, and Fort Erie, Ontario, where it crosses the Niagara River. The bridge opened in 1927 to commemorate 100 years of peace between Canada and the United States. It is North America’s sixth busiest border. About $1 billion U.S. in trade crosses the bridge weekly. More than 5,000 commercial vehicles cross the bridge each day.