Ontario was discovered by Etienne Brulé and Samuel de Champlain in 1610 when they went down the St.Lawrence River. Then came the British in the form of Henry Hudson. Hudson named the bay that he came into Ontario after himself. To keep the French from kicking him out Hudson built forts to protect British interest with the fur trade. The British and the French fought one another for some years with the British victorious after the Seven Years War. The Treaty of Paris in 1763 gave the British all that was claimed by the French.
When the Revolutionary War broke out in the American Colonies many loyalist move to what would become Ontario. Then in 1791 the British put into law the Constitutional Act, which split up the territory called Quebec into the providence of Ontario and Quebec. Ontario's capital was established in Newark, but it was changed to what would become Toronto for more protection from the outside world.
During the War of 1812 United States troops came up to Toronto and burnt down the capital building. The Canadians didn't like this so they went to Washington D.C. and burnt the White House down. The war ended with the signing of the Treaty of Ghent. The British gave up some territory and were welling to help end the slave trade.
The population in Ontario was growing and trade was getting faster. Canals between the Great Lakes helped trade move faster. The people of Canada were angry because they were being ruled by only a select few people and the people started to have revolts. To stop the continuation of this problem the Union Act was introduced which reconnected Quebec and Ontario into the Providence of Canada. Not that effective because it put the French Canadians as minority and had the capital Montreal. Quebec and Ontario split then reformed with Nova Scotia and New Brunswick to form the Dominion of Canada. The national capital was placed in Ottawa.
Resources:
http://www.gov.on.ca/ont/portal/!ut/p/.cmd/cs/.ce/7_0_A/.s/7_0_252/_s.7_0_A/7_0_252/_l/en?docid=004523
http://www.ourdocuments.gov/doc.php?flash=false&doc=20