SR 73 begins in St. George at SR 131 about north of Marshall Point. SR 73 runs roughly parallel to SR 131 on the coastline, passing through the towns of
South Thomaston and
Owls Head without any major junctions. SR 73 crosses into
Rockland and proceeds due north into the town center, where it ends at US 1. SR 73 is known as Seal Harbor Road in St. George, Spruce Head Road in
Spruce Head, Elm Street in South Thomaston, and Weskeag Road, Ingraham Drive and South Main Street in Rockland.
Knox County Regional Airport is located along SR 73 in Owls Head. ==Junction list==