The following article is based on one in Wikipedia.
Peel County is an historic county in the Canadian province of Ontario, named for Sir Robert Peel (1788-1850), Prime Minister of Great Britain. Its boundaries were established in 1849 and achieved its own local government in 1851. Prior to that it had been a portion of York County. Settlers had arrived in Toronto Township as early as 1807. The Credit River valley to the north was reserved for the Mississauga First Nation, however they sold their land and moved to the Bruce Peninsula.
Peel was divided into five townships. A diagramatic map in Wikipedia shows the location of each and a map of Peel County circa 1951 from Ontario Archives locates the individual towns and villages.
In 1973, Peel County became the Regional Municipality of Peel, as a result of the Ontario provincial government's regionalization of the rapidly developing counties surrounding Toronto. The council of the regional municipality follows the township structure of the former county.
Following the reorganization Peel Regional Municipality had three divisions (listed from south to north):
The primary source for basic documents (vital statistics, land records, wills) for people who lived in the Province of Ontario is the Archives of Ontario, 134 Ian Macdonald Blvd, Toronto, Ontario, Canada M7A 2C5.
Civil registration did not begin in the province until 1869. Before then there may be church records of baptisms and burials. For the most part these are still held by the denomination who recorded them. Copies of marriage records made pre-1869 had to be sent by individual clergymen to the registrar of the county in which the marriage took place. These marriage records are available through Ontario Archives, on micorfilm through LDS libraries, and on paid and unpaid websites, but because they were copied at the registrars' offices, they cannot be considered a primary source.
Vital Records after 1869
Birth, marriage and death registrations are not open to the public until a specific number of years after the event occurred. Births to 1914 are now available [October 2012]; dates for marriages and deaths are later. Birth and death registration was not universally carried out in the early years after its adoption. Deaths were more apt to be reported than births for several years. The more rural the area, the less likely it would be that these happenings were reported to the authorities.
Land Records and Wills
Information on how to access land records and wills is best sought on the Archives of Ontario website. An ancestor's land holding might be found on Canadian County Atlas Digital Project if he was in occupancy circa 1878.
Association for the Preservation of Ontario Land Registry Office Documents (APOLROD). A list of Land Registry Offices for all Counties of Ontario.
The original censuses are in the hands of Library and Archives Canada. All of the original census (1851-1911) images are online with the exception of that for 1861. Not all of them are indexed. Later censuses are not yet available. Census divisions were redrawn as the population increased and more land was inhabited.
E-books and Books
Some websites with more local information on Peel County
Source: Province of Ontario -- A History 1615 to 1927 by Jesse Edgar Middleton & Fred Landon, copyright 1927, Dominion Publishing Company, Toronto