Several helpful guides to places in Ontario have been published. The Family History Library Catalog usually lists records according to the jurisdictions indicated in this most useful modern gazetteer:
Gazetteer of Canada: Ontario. 1962 edition. Ottawa, Ontario: Department of Mines and Technical Survey Geographical Branch, 1962. (FHL book 971.3 E5c; not on microfilm.) This edition was published before regional municipalities had been erected out of some former townships and counties. Lists localities alphabetically and references the township and county in which each was located. Gives geographical coordinates (latitude and longitude). Note: Newer editions omit all references to jurisdictions such as townships and counties and merely list the latitude and longitude of each locality.
For recent jurisdictions in which many localities are found, see:
Schindler, Marc A. Administrative Atlas of Canada; Vol. 3: Ontario. Gloucester, Ontario: Schindler-Spring Family Organization, 1988. (FHL book 971 E7sm v. 3; not on microfilm.) This volume has a gazetteer that lists major towns and the jurisdictions they are in. It has schematic maps that show the boundaries of those jurisdictions.
Historical Place Names
Because names and boundaries of some places have changed or no longer exist, you may need to use sources that describe places as they were known earlier. Old and new names of many localities are in:
Carter, Floreen Ellen. Place Names of Ontario. London, Ontario: Microfilmed for Phelps Publishing Company by David Hallan Information Graphics, 1985. (On 25 microfiches; FHL fiche set 6332553. No circulation to Family History Centers.) Reports that Ontario places averaged three name changes through history. Includes a cross-reference index to all place names, old and new.
An excellent source of information on localities and their jurisdictions in early Ontario is Lovell's Canadian Dominion Directory for 1871. See the "Directories" section of the Canada Research Outline (34545).