SR 173 was commissioned in 1923, originally routed from SR 19. northeast of Louisville, to SR 19, south of Beloit.[2][3] In 1927 the route was rerouted onto the route of previous SR 19, through Alliance.[4][5] The route was extended west to its current western terminus, at SR 44, in 1937.[6][7] Between 1969 and 1971, SR 173 was rerouted concurrent with US 62 from west of Alliance to Salem.[8][9] In 1976 US 62 in Salem was rerouted to bypass the city and SR 173 remained on the old route of US 62.[10][11]
^ abOhio Department of Highways and Public Works (July 1923). Map of Ohio Showing State Routes(PDF) (Map). 1:760,320. Columbus: Ohio Department of Highways and Public Works. Retrieved September 24, 2013.
^Ohio Department of Highways and Public Works (August 1, 1926). Map of Ohio Showing State Routes(PDF) (Map). 1:760,320. Columbus: Ohio Department of Highways and Public Works. OCLC5673562. Retrieved September 24, 2013.
^Ohio Department of Highways and Public Works (June 1, 1927). Map of Ohio Showing State Routes(PDF) (Map). 1:760,320. Columbus: Ohio Department of Highways and Public Works. OCLC5673562. Retrieved September 24, 2013.
^Ohio Department of Highways (1936). Official Highway Map of Ohio(PDF) (Map). 1:760,320. Columbus: Ohio Department of Highways. OCLC5673562. Retrieved September 24, 2013.
^Ohio Department of Highways (1969). Official Highway Map(PDF) (Map). c. 1:563,200. Columbus: Ohio Department of Highways. OCLC5673562, 7448779. Retrieved September 24, 2013.
^Ohio Department of Highways (1971). Official Highway Map(PDF) (Map). 1:554,400. Columbus: Ohio Department of Highways. OCLC5673562. Retrieved September 24, 2013.
^Ohio Department of Transportation (1975). Ohio Transportation Map(PDF) (Map). 1:554,400. Columbus: Ohio Department of Transportation. OCLC5673562. Retrieved September 24, 2013.