Ancient times
Unlike other Canadian cities and regions, it's quite hard to name and characterize a single ancient culture that would have lived in the area of today's Toronto. The truth is that the existence of an ancient permanent settlement is unlikely, and even if there was, we'd have a very hard time looking for artifacts from this period - most of it would lie on the bottom of Lake Ontario, as the shoreline was located 20 km south. All the information we have is that various tribes, including the Mohawks, Erie, Senecas, Cayugas, Oneidas and the Wendat, had various uses for this region including hunting and season-dependent camps. Toronto as a name most likely comes from a Mohawk word tkaronto, which would mean "a place where trees stand in water".
Settlement
It is unclear when did Europeans reach the area of today's Toronto first, but a French explorer, Etienne Brule, is the first person credited to stand on the shores of Lake Ontario. It was a crucial site because of the shortcut between Lake Ontario and the upper Great Lakes, as well as for its series of water routes which allowed to travel from the northern and western areas of Canada to the Gulf of Mexico. Soon enough, it has become a vital junction for fur trading. Later, this fact has led to a fight between Britain and France as they tried to gain control.
Governor Simcoe
John Graves Simcoe went down in history as the godfather of Toronto, named York at first (the name was changed because of the distinction between New York City and other provinces named similarly). He viewed the settlement as a key element in guarding the American border. Soon, it has became the capital of Upper Canada and the need for routes (mainly for military communication) has led to the creation of three major roads - Yonge Street, Kingston Road and Dundas are all present today and the first is renowned for being the longest street in the world, running 1896 kilometres to the Rainy River.
American raids on York
During the war of 1812, York was raided two times and it was even taken for a brief moment. Fort York has been partially burned in 1813, when Pike Zebulon attacked it with his troops. British soldiers were outnumbered by many and decided to retreat, yet still stop the attack by setting fire to all magazines in the fort. The explosion occurred just when the Americans entered the building, killing zebulon and many of his man in action. After the American armed forces left, it was rebuilt much stronger and the attackers didn't even had the chance to reach the shore.
The Great Irish Famine
The mid 1800's saw a large number of Irish immigrants, both Catholic and Protestant. The latter group was more successful and soon started playing a major role by occupying major positions in politics, education and business. This has led to many conflicts with their Catholic counterparts, and escalated into several big riots including the infamous Julibee Riot of 1875.
Population growth
Toronto's population was only 720 in 1812. This number has multiplied by nearly 8000 times since, reaching 5,550,000 in 2006 (counting the metropolitan area). There were several periods of intense immigration, peaking after the second World War, which brought more than one million new inhabitants from the war-torn Europe, especially Germans, Italians, Russians, Poles and Jews from various parts of the old continent. To date, Toronto is one of the most multi-cultural cities in the world.
The first trains and transportation
1853 was the year when the first trains pulled out of Toronto on a long track that ran north to Barrie on Lake Simcoe. In the end, Toronto became the main railway hub for Western Canada, further enhancing the importance of the city. By this time, Toronto had already distinct neighbourhoods, a drain system, piped water, gas lightning and a very healthy economy.
Industrialization
British industrial advances and a reciprocal free trade agreement with the United States has led to major developments in Canada, including Toronto. Coal-fired steam power was used to produce an extensive range of products, which were shipped by train and on water, the latter transforming the city's harbor into a grimy and sedulous industrial zone.
CN Tower
In the late 60, the city was experiencing a major real estate boom and skyscrapers were being built rapidly in the centre. As they were blocking radio and TV signals, and the only solution was to raise the antenna above all of them. It was completed in 1975 and it's still Toronto's main tourist attraction and it was the tallest free standing man-made structure on Earth until very recently.
Epidemics
There were several larger scale epidemics that threatened Toronto during it's relatively short modern history. Cholera stuck out it's deadly head three times (1832, 1834 and 1849), followed by typhus and most recently the SARS outbreak of 2003. The latter had a profound negative effect on tourism, mainly due to exaggerated media reports (the disease only presented a realistic danger to workers in medical-care).
The Great Blackout of 2003
As a part of a large-scale blackout in North America, Toronto had no electricity for more than 24 hours, reaching several days in some areas. Passengers had to be evacuated from the Subway and walk out from the tunnels. Civilian volunteers had to help the police coordinate traffic and bigger objects had to be illuminated by emergency lights in order to not present dangers to ships and other vehicles passing by.