Wikipedia:WikiProject U.S. Roads/Montana/All-time list

Given are the years of the first and last official maps (also is a little blurry but has a few that aren't on the MDT site) the routes appear on. These are not always the exact years the routes were created or eliminated.

A 1927 and 1930 map and a 1929 map show an almost completely different numbering system.

A 1932 Gousha/Conoco map shows some routes; these are marked with an asterisk. Note that all except 22 (which was kept in the numbering system) were odd.

Secondary routes first appear on maps in 1960, but federal aid logs are available back to 1938 (1943 is the first with secondaries) (post-1993 logs). Therefore all secondary years are based on the logs, but primary years are based on maps.

haven't gone through these: 2011 log 2013 log