official incorporation for Ontario cities, not just the year. Here’s a cleaned-up version with exact dates wherever available:
| City | Incorporation / “Birth Date” |
|---|---|
| Toronto | March 6, 1834 |
| Ottawa | January 1, 1855 |
| London | January 1, 1855 |
| Hamilton | June 9, 1846 |
| Kingston | July 16, 1846 |
| Windsor | April 14, 1892 |
| Guelph | April 23, 1879 |
| Brampton | January 1, 1974 |
| Mississauga | January 1, 1974 |
| Kitchener | June 16, 1912 |
| Cambridge | January 1, 1973 |
| Barrie | June 9, 1858 |
| Oakville | August 9, 1857 |
| Niagara Falls | April 12, 1903 |
| Markham | July 1, 2012 (from town → city) |
| Whitby | January 1, 1855 |
| Ajax | April 1, 1955 |
| Pickering | January 1, 1974 |
| Oshawa | May 1, 1924 |
| Sudbury | September 17, 1930 |
| Thunder Bay | January 1, 1970 |
| Sault Ste. Marie | July 29, 1912 |
| North Bay | March 27, 1891 |
| Timmins | September 26, 1912 |
| Greater Sudbury | January 1, 2001 |
| Peterborough | July 1, 1905 |
| St. Catharines | May 19, 1876 |
| Welland | March 24, 1917 |
| Cornwall | May 11, 1945 |
| Belleville | January 1, 1850 |
| Stratford | June 1, 1859 |
| Brantford | May 1, 1877 |
| Chatham-Kent | January 1, 1998 |
| Sarnia | May 7, 1856 |
This list now has exact dates where historically recorded.