Understanding the geographical changes in Ontario's borders can assist anyone researching in Ontario. Following is a brief overview of the changes in boundaries and name changes for present-day Ontario.

• In 1615 Champlain and Brule explored what is now southern Ontario.

• Present day northern Ontario was part of the territory given to the Hudson's Bay Company.

• In 1673 Frotenac founded Cataraqui (near present day Kingston)

• The British captured Fort Niagara in 1759

• Prior to December 26, 1791 Ontario was known as the Western part of the Montreal District of the Colony of Quebec.

• 1783 saw the arrival of the first United Empire Loyalists (UEL)

• In 1788 present-day southern Ontario was divided into four districts: Hesse, Lunenburg, Mecklenburg and Nassau

• In 1791 the colony of Quebec was divided into the two provinces of Upper and Lower Canada. Upper Canada (now Ontario) was all that land lying west of the Ottawa River, while Lower Canada (now Quebec) was all the land lying east.

• In 1792 the first parliament began. The four original district names were changed. Hesse became the Western District; Lunenburg became the Eastern district; Mecklenburg became the Midland district and Nassau became the Home District.

• In 1800 the districts were divided into counties

• In 1812 war broke out with the United States (The War of 1812). At this time approximately 2/3 of the population of present-day Ontario were non-loyalists who had been attracted by offers of free land

• In 1813 during The War of 1812, the town of York (present day Toronto) was burned. Newark (Niagara) was also burned. Many records were lost.

• 1815 saw large immigration from Scotland to Lanark County.

• 1820-1850 saw large numbers of immigrants from Great Britain

• 1833 saw over 66,000 British immigrants arrive, many via the Erie Canal from the port of New York

• In 1842 Upper and Lower Canada united to form the Province of Canada. Upper Canada (present-day Ontario) became known as Canada West while Lower Canada (present day Quebec) became known as Canada East. For complete details consult Districts of Canada West in 1846

• In 1843 fire destroyed government records at York

• In 1867 Upper Canada, or Canada West was given the name of the province of Ontario. It was one of four original provinces at the time of Canadian Confederation on July 1, 1867.

• 1868 The Rupert's Land Act admitted it to the Dominion of Canada. Rupert's Land was originally owned by Hudson's Bay Company and consisted of part of the present-day provinces of Ontario and Quebec North of the Laurentians and West of Labrador; all of Manitoba; most of Saskatchewan; the southern half of Alberta; the eastern part of Nunavut Territory; and portions of Minnesota and North Dakota in the United States.

• In 1912 Ontario's boundaries moved northward to Hudson Bay

• In 1916 fire destroyed the Center Block of the Parliament Buildings in Ottawa