By the 1930's and 1940's, all of the streetcars were replaced with buses, except in a few of the largest cities. Some bus systems continued to be owned by power companies, other bus systems were owned by various different types of companies of different sizes. And by the end of the 1970's, nearly all transit systems were publicly owned. Although many transit agencies would contract with private transit management companies to operate the transit systems.
Most transit systems became owned by the cities served. Although in certain larger metropolitan areas, regional transit authorities were approved by the states and the voters to develop comprehensive transit systems serving both cities and suburbs.
All-Time List of Canadian Transit Systems
While this web site attempts to provide comprehensive coverage of the US, the linked web site here provides comprehensive coverage of Canada.
For the transit systems in the largest cities, the goal is to relate the bus routes of the publicly owned transit systems to the past. Relate the bus routes to the past streetcar and bus companies, tracing the route history back to the beginnings of public transportation in that area. At times it can be fascinating, untangling the sometimes complex transit histories, especially in areas where multiple transit companies operated.
For each city covered, the information on this Web site is by no means complete. Emphasis is on routes which evolved from streetcar and bus routes introduced by the private transit companies. And many bus routes introduced by the publicly owned transit agencies are not listed. Availability of information is usually dependent on how much has been published about the different city transit systems. In many cases, the history covered focuses on prior to the public takeover of many transit systems.
For the Midwest cities, historic streetcar and bus rosters are included. Historic bus roster information usually is provided up to around the year 2000. For more contemporary bus roster information, links are generally provided to other web sites.
Canadian Public Transit Discussion Board
This web site seems to contain some of the most up to date bus roster information throughout the country.
In addition, many major cities have a Wikipedia page, linked from the pages here covering those cities. These Wikipedia pages usually contain the most recent bus roster information available, and additional timely information. But of course any information on the Web, including this web site, cannot be solely relied on for all of the absolute facts.