Milemarker 120E at OR-31/US-395 junction. These type of milemarkers with the letter suffix have started to appear around Oregon. The letter indicates the segment of highway that the mileage is for. In Oregon, mile markers are posted according to internal highway, not posted route number (except for intersate highways). In this case the milemarker is for Fremont Highway. A posted highway can be composed of have multiple segments of internal highways. The milemarker in this photo is for the 5th (E is the 5th letter) segment of internal highway along posted route US-395. See here for more discussion: en.wikipedia.org/wiki/State_highways_in_Oregon#Highways_a…