The Toronto Reference Library’s Marilyn and Charles Baillie Special Collections Centre (formerly the Baldwin Room), the Archives of Ontario, the City of Toronto Archives, and Library and Archives Canada each have collections (fonds) of personal and business papers from Toronto.
Whether or not your ancestor left a collection of papers, he or she could be mentioned in those of a contemporary. Watch for names from your ancestor’s neighbourhood, ethnic group, workplace, fraternal organization, or anyone one who lived in the same place at the same time as your ancestor. Even if you don’t find your ancestor’s name, you’ll get a picture of what their world was like.
The Toronto Reference Library’s manuscript catalogue is in a variety of formats, and must be consulted in person. However, their collection does emphasize early Toronto. More information about the collection can be found here. A published catalogue of material acquired before 1954 is available here. A simple listing of manuscript titles—including more recent material—with links to the pre-1954 catalogue where applicable is available online here, but to really understand the contents, be sure to consult the card catalogues and any additional finding aids noted when you visit.
All manuscript fonds at the Archives of Ontario are listed on the Archives Descriptive Database. Some are described in great detail and names can be searched. If the fonds has been microfilmed it may be available for interloan to a library closer to you.
The City of Toronto Archives lists manuscripts in a computerized database available on its web site.