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
City status in the United Kingdom Since local government reorganisation in 1974 city status has been awarded to a number of local government districts which are not themselves towns. Each includes a number of towns and villages outside the urban area from which the district takes its name. In some of these cases city status was awarded to districts where the largest settlement had city status before 1974. In other cases a borough was formed to govern an area covering several towns and then city status was granted to the borough. The largest "city" district in terms of area is the City of Carlisle, which covers