List of auto trails in Maine

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Auto trails in Maine
System information
Maintained by MaineDOT
Highway names
InterstatesInterstate x (abbreviated I-X)
US HighwaysU.S. Route x (abbreviated US-X)
StateState Route x or Route x (abbreviated SR X)
Lettered routesRoute x
System links

Beginning in 1914, Maine used a system of lettered highways to designate cross-state routes; however, these were internal designations, never meant to be signed for use by drivers. In 1919, the Maine Automobile Association and the Maine State Highway Commission collaborated to create a series of state-designated auto trails specifically to aid public navigation.[1] The system posed a stark contrast to the auto trail systems of other states, which were often private endeavors, with improvements by these booster organizations ranging from simple marked poles to paving and maintenance of the road. This system was abandoned by 1925 in favor of the New England interstate highway system.[2]


It is unclear which routes listed below existed at what times.

Route Colors From Through To Lettered route Replacement (1925) Modern designation Notes
Atlantic Highway Blue New Hampshire Line Kittery, Wells, Kennebunk, Scarborough, Portland, Yarmouth, Brunswick, Bath, Wiscasset, Waldoboro, Rockland, Belfast, Searsport, Bangor, Ellsworth, Hancock, Millbridge, Jonesboro, Machias, Dennysville, Perry, Robbinston Calais A, C, D, L, M, N Route 1 US 1
Longfellow Highway Yellow New Hampshire Line Bethel, Bryant Pond, West Paris, South Paris, Norway, Poland, Gray Portland O, S Route 15 US 2, SR 26
Theodore Roosevelt International Highway White



New Hampshire Line Fryeburg, Bridgton, Naples, Raymond, North Windham, Highland Lake Portland B Route 18 U.S. 302
Grafton Notch Highway White


New Hampshire Line Upton, Newry Bethel T, O Route 26 US 2
International Trail Red Brunswick Gardiner, Augusta, Waterville, Skowhegan, Norridgewock, Anson, Solon, Caratunk Plt, Jackman Station Canada (Québec) Line Q, H Route 20 U.S. 201, U.S. 201A
Aroostock Trail White


Fairfield Clinton, Pittsfield, Newport, Bangor, Old Town Lincoln I, K Route 100, 15, (24) US 2, (US 1) 1923: Extended to Houlton, then Mars Hill, Presque Isle, Caribou, Van Buren, Madawaska to Canada (New Brunswick) Line
Capital Way Blue


Portland Lewiston Augusta E Route 100 SR 100, US 202
Kennebec-Penobscot Trail Orange


Augusta South China, Liberty, Searsmont, Belmont Belfast R Route 102 US 202, SR 3
Mount Desert Trail Yellow


Ellsworth Hulls Cove Bar Harbor M Route 183 SR 183, SR 3
Brunswick-Greenville Highway Green


Newport Dexter, Dover, Guilford, Abbott, Monson Greenville J Route 104 SR 7, SR 23, SR 6
Poland Springs-White Mountain Trail Green Naples Casco, Poland Mechanic's Falls Route 116 SR 111


  1. ^ Nelson, Lyman H.; Deering, Philip J.; Ayer, William M. (1919). Seventh Annual Report of the State Highway Commission of the State of Maine (7th ed.) – via Google Books.
  2. ^ Kaiser, Cameron (2007). "Maine's Lettered Highways (1913)". RoadGap. Retrieved November 15, 2019.