Greater Toronto Area (the GTA) is the most populous metropolitan area in Canada. The GTA has a population of over 5.7 million people (July 1, 2005). In addition to the City of Toronto, it includes the Regional Municipalities of York, Halton, Peel and Durham. The term GTA only came into usage in the mid-1990s after it was used in a widely discussed report on municipal governance restructuring in the region.

The Greater Toronto Area is one of North America's fastest-growing urban areas. As an economic area, the GTA consists of 25 municipalities and four regions in a total area of over 7,000 km². This translates into one of the lowest densities for an urban area in the world at 800 people per km², although it might be noted that vast parts of the GTA remain farmland and forests including protected sections of the Oak Ridges Moraine and the Niagara Escarpment. Nevertheless, low density suburban developments continue to be built, some on or near ecologically sensitive and protected areas. The government of Ontario has recently attempted to address this issue through the "Places to Grow" proposal which emphasizes higher-density growth in existing urban centres over the next 25 years.

The work force is approximately 2.9 million people, more than 100,000 companies and a $360 billion CAD gross domestic product, the GTA is Canada's undisputed business and manufacturing capital. The GTA is home to a number of post-secondary educational institutions, including 4 universities and 7 colleges.

Some municipalities that are considered part of the GTA are not within the Toronto Census Metropolitan Area (CMA) (population est. 5,304,100 in 2005), example Oshawa, which is the centre of its own CMA or Burlington, which is included in the Hamilton CMA, therefore the GTA's population is higher than the Toronto CMA by almost one-half million people, often leading to confusion amongst people when trying to sort out the urban population of Toronto.

Other nearby urban areas, such as Hamilton, Barrie or Kitchener-Waterloo are not part of the GTA, but other CMA's (Census Metropolitan Area) in close proximity to the GTA. Ultimately, all the aforementioned places are part of the Greater Golden Horseshoe, the sixth most populous urban agglomeration in North America with nearly 8 million residents.

The following regional governments are included in describing the Greater Toronto Area:

• Regional Municipality of Durham
• Regional Municipality of Halton
• Regional Municipality of Peel
• Regional Municipality of York

The City of Toronto is now a single-tier municipality, but before 1998 it had a similar "regional" structure under the name Metropolitan Toronto.

The City of Hamilton, Regional Municipality of Niagara and City of Guelph all have significant ties to Toronto and the Greater Toronto Area. Nonetheless, they are geographically distant enough not to be considered part of the GTA, officially or otherwise. It is expected that with current rate of regional growth these areas will one day in the future become part of the Greater Toronto Area. In some cases the provincial government already includes Hamilton and Niagara as part of the GTA for record keeping purposes as well as for transportation planning.

In 2001, Statistics Canada identified four major urban regions exhibiting a cluster pattern of concentrated population growth. Among these regions, the Extended Golden Horseshoe Census Region includes all of the Greater Toronto Area listed above, as well as Niagara, Hamilton, Guelph and Kitchener-Waterloo. Combined, the Extended Golden Horseshoe has a population of more than 6.7 million people, now estimated at 7.8 million, containing approximately 21% of Canada's population.

Area codes

The Greater Toronto Area is served by six distinct area codes. Before 1993, the Golden Horseshoe used the 416 area code. In a 1993 zone split, the City of Toronto retained the 416 code, while the rest of the Greater Toronto Area was assigned the new area code 905. This division by area code has become part of the local culture to the point where local media refer to something inside Toronto as "the 416" and outside of Toronto as "the 905". Though for the most part this was correct, it isn't entirely true as some portions of Durham Region are use the area code 705, and some portions of Halton and Peel Regions are use the area code 519. Furthermore, there are areas, such as Port Hope, Ontario, that use the 905 area code, but are not part of the GTA, or even the Greater Golden Horseshoe.

To meet the increased demand for phone numbers, two overlay area codes were introduced in 2001. Area code 647 (supplementing the 416 area code) was introduced in March 2001 and area code 289 (supplementing the 905 area code) was introduced in July 2001. As well, individuals within the 905 area code region may have to dial long distance to reach each other; although residents of Mississauga and Hamilton share the same area code (905), an individual from Toronto, for example, would have to dial "1" (long distance code before 905) to reach Hamilton, but not to reach Mississauga. Ten-digit telephone dialing, including the area code for local calls, is required throughout the Golden Horseshoe region. As of October 21, 2006, the 519 area code will have an overlay area code of 226.

Transportation

Most of the GTA is served by GO Transit, a regional transportation authority that connects Toronto's suburban areas to its downtown. The GTA also has the largest and busiest freeway network in Canada, consisting mainly of 400-Series Highways and supplemented by municipal expressways.

A list of public transit operators in the GTA:

• Toronto Transit Commission - Toronto, Markham, Richmond Hill, Vaughan
• York Region Transit - Markham, Ontario, Richmond Hill, Ontario, Vaughan, Ontario
• Durham Region Transit - Pickering, Ajax, Whitby, Oshawa, Clarington, Brock, Scugog, Uxbridge
• Mississauga Transit - Mississauga, Brampton, Toronto, Oakville
• Brampton Transit - Mississauga, Brampton, Toronto, Vaughan
• Oakville Transit - Oakville, Mississauga
• GO Transit - inter-regional service

A list of major roadways in the GTA:

• 407 ETR - York Region, Peel Region, Durham Region
• Highway 403 (Ontario) - Peel Region, Halton Region
• Highway 427 (Ontario) - York Region, Toronto
• Highway 410 (Ontario) - Peel Region
• Highway 409 (Ontario) - Toronto
• Highway 404 (Ontario) - York Region, Toronto
• Highway 401 (Ontario) - Durham Region, Toronto, Peel Region, Halton Region
• Highway 400 (Ontario) - York Region, Toronto
• Highway 7 (Ontario) - York Region, Peel Region, Durham Region
• Queen Elizabeth Way - Peel Region, Halton Region
• F.G. Gardiner Expressway - Toronto
• Don Valley Parkway - Toronto
• Allen Road - Toronto

Politics

There has been a growing tension between Toronto and the surrounding GTA area since the mid 1990s, with Toronto complaining that it has been economically exploited by its neighbours. The election of the Harris government was attributed to his support base in the suburban "905" region. During his time in office, many provincial services were downloaded to the municipal level, which caused great financial strain on an already indebted city. Although the succeeding McGuinty government has attempted to address this imbalance, Torontonians feel that his attempts are half-hearted because McGuinty also had significant "905" support during his 2003 election victory.

Most of the "905" municipalities have few cultural institutions, despite their significant populations. For instance, Mississauga is one of the largest cities in Canada by population but has no daily newspaper, television stations, or commercial radio stations. Despite having attracted significant investment over the last few decades, the surrounding cities are still considered bedroom suburbs of Toronto rather than independent municipalities, and as a result many are virtually unknown outside of Ontario. Prior to the municipal amalagamations that took place with the introduction of regional government, Oshawa was the only nearby city with a significant population and recognition.