Beginning in 1927, intrastate bus service was regulated by the Wisconsin Railroad Commission, or Wisconsin Public Service Commission after 1931. Although some limited regulation actually began in 1915.
Prior to regulation, the publication "Bus Transportation", with their May 1922 issue, listed the bus lines in operation at the time.
These lists focus mainly on interurban and intercity bus routes. And for local city transit systems, the following lists generally only indicate the first bus service either supplementing or replacing some streetcar service.
A consistent numbering system never existed for the Certificates of Convenience and Necessity. Several different numbering systems were used, preceded with different combinations of letters. And not all certificates were documented, especially those "grandfathered" from earlier bus routes. Some certificates might have been renumbered without being documented, some certificate numbers and case numbers might have been confused. Every effort was made to reconstruct all awarding of certificates. This list is in the general order in which the certificate sequences were awarded.
For routes where the certificates were not documented, the years of introduction or transitions were compiled from various issues of the magazine "Motor Coach Age". This information is where a year is included without an exact date.
Cases Identified as Bonded Carrier Cases
Cases Identified as Auto Transportation Cases (First Group)
Cases Identified as Auto Transportation Cases (Second Group)
Miscellaneous Certificates
Later Certificates 1930's
Later Certificates 1940's-1970's
By the mid 1930's, a standard numbering system was adopted for certificates, and older certificates were assigned numbers from this series.
In the early 1920's, prior to regulation, numerous bus lines were created to supplement, and later replace the extensive interurban railway system in Milwaukee and southeastern Wisconsin.