North America metropolitan area by population in North America: Greater Mexico City. Canada also breaks into the top ten largest metropolitan areas with the Toronto metropolitan area having six million people. The proximity of cities to each other on the Canada–United States border and Mexico–United States border has led to the rise of international metropolitan areas. These urban agglomerations are observed at their largest and most productive in Detroit–Windsor and San Diego–Tijuana and experience large commercial, economic, and cultural activity. The metropolitan areas are responsible for millions of dollars of trade dependent on international freight. In Detroit-Windsor the Border Transportation Partnership study
Portages in North America major street is named "promenade du Portage" as the city is the head of uninterrupted navigation from Montréal on the Ottawa River and one must portage around the Chaudière Rapids. Portages in North America Trails around portages in North America usually began as animal tracks and were improved by tramping or blazing. In a few places iron-plated wooden rails were laid to take a handcart. Heavily used routes sometimes evolved into roads when sledges, rollers or oxen were used, as at Methye Portage. Sometimes railways were built (Champlain and St. Lawrence Railroad). The basic purpose of most canals is to