Beginning in 1921, intrastate bus service in Maine was regulated by the Maine Public Utilities Commission. Information could not be located, regarding the issuance of Certificates of Convenience and Necessity for bus service. But the October 1922 issue of the publication "Bus Transportation" included a table listing the bus routes in existence in Maine.
Not listed are city bus routes, along with bus routes of a more suburban or local nature.
This information does not include the actual bus companies operating the routes. And it was not possible, to establish how these companies became part of the Greyhound or other larger bus companies.
Bangor-Frankfort Buckfield-Berlin NH Farmington-Eustis Farmington-New Sharon Farmington-Phillips-Rangeley Greenville-Bangor Greenville-Duck Pond Greenville-Lily Bay Greenville-Kokadjo Lewiston-Old Orchard Rumford-Bryant Pond Rumford-Lewiston