Ontario, most populous and wealthiest province in Canada. It is the nation's leader in manufacturing, mining, and agriculture. Ottawa, the nation's capital, and Toronto, the province's capital and the nation's second-largest city, are located in Ontario. The economic heart of Canada, Ontario accounts for 40% of the nation's productive capacity. Its industrial output is equal to that of the rest of the country combined.
Ontario can be divided into 4 physical regions. In the north lies the sparsely populated Hudson Bay Lowland, a flat, wet, rocky plain covered with forests, tundra, and swamps. To the south is the Canadian Shield, extending from the Manitoba border to the Ottawa River and covering over half of Ontario's surface with hard rock. Although it supports little agriculture, the Canadian Shield region is one of the greatest sources of mineral wealth in the world. The Great Lakes Lowland lies along Lakes Huron, Erie, and Ontario. Most of Ontario's population, cities, and industries are located on this peninsula, which is also the site of the region's richest farmland. The fourth and smallest land region is the St. Lawrence Lowland, a triangular area of low hills and fertile valleys between the Ottawa and St. Lawrence rivers, in the extreme eastern corner of the province.
Water covers one-sixth of Ontario's surface. On the Ontario-United States border lie 4 of the 5 Great Lakes, the largest group of freshwater lakes in the world. In the interior of the province are some 250,000 lakes, most in the Canadian Shield. The St. Lawrence, the chief river in Ontario, has become a great international seaway since the construction of the St. Lawrence Seaway. The Detroit, St. Clair, and St. Marys rivers, which connect the upper Great Lakes, are important shipping routes. Ontario's rivers supply 90% of the province's electricity.
Ontario is responsible for about half of Canada's manufactured goods, a third of its agricultural wealth, and a fourth of its mineral production. Highly industrialized cities such as Toronto manufacture cars, iron and steel products, and petrochemicals. In the Great Lakes Lowlands, specialized and highly productive farms grow crops such as hay, tobacco, soybeans, oats, tomatoes, and corn. Rich orchards and vineyards lie in the Niagara fruit belt. In the northeastern part of the Great Lakes Lowlands, beef and dairy cattle are reared. Ontario also provides about 20% of Canada's commercial lumber.
Ontario's first significant settlement was in the 1780s, when thousands of American Loyalists made their homes along the Niagara, Detroit, and St. Lawrence rivers. The Constitutional Act of 1791 gave the settlement a British form of government. Struggles for political reform culminated in the Rebellion of 1837–38 and resulted in Britain's decision to reunite the regions of Ontario and Quebec. With the historic British North America Act of 1867, the Dominion of Canada was formed; its 4 original members included Ontario, Quebec, New Brunswick, and Nova Scotia. Ottawa became the first federal capital, and Sir John A. Macdonald of Ontario the first prime minister. During World War II Ontario experienced a great burst of industrial growth, and the pace of development accelerated as huge deposits of uranium, copper, zinc, and silver were found. The province's prosperity has attracted more than half of the 3 million European immigrants that have come to Canada since World War II.