Canada celebrates Canada Day. Formerly called Dominion Day, the national holiday marks the 1867 union of Upper and Lower Canada and some Maritime Provinces. Slightly larger than the United States, Canada borders three oceans: Pacific, Atlantic, and Arctic. According to the CIA World Factbook, Canada is the largest country that borders only one country, in this case the United States. More than 34 million live in Canada, and most of those people live along its southern border. Ottawa is the capital.