Ohio State Route 309
|Maintained by ODOT|
|Length:||103.20 mi (166.08 km)|
|Existed:||1973 – present|
|West end:||US 30 near Delphos|
| I‑75 near Lima
US 68 in Kenton
US 23 near Marion
|East end:||US 30 in Mansfield|
|Counties:||Allen, Hardin, Marion, Morrow, Crawford, Richland|
State Route 309 (SR 309) is an east–west highway in central Ohio. Its western terminus is at its interchange with U.S. 30 near Delphos, Ohio, and its eastern terminus is at its interchange with U.S. 30 in Mansfield, Ohio. Its current route takes it through the cities of Lima, Kenton, Marion, Galion, and Ontario; as well as the villages of Elida and Caledonia.
SR 309's current route was the route of U.S. Route 30S, a divided U.S. route of US 30 until November 1973 when what was US 30N became the mainline of US 30. US 30S was so numbered in the 1920s to avoid conflict from local business owners worried about the diversion of traffic from their shops along the southern route.
The only significant change of the route since this certification is its western terminus, which originally was with U.S. 30 in Delphos. When U.S. 30's bypass around Delphos was completed in 1981, Ohio 309's western terminus was made the easternmost interchange of the bypass.
The Lincoln Highway left the present State Route 309, a better-quality road at the time, in favor of the direct Delphos-Mansfield route now generally followed by US 30. Only two weeks after the official route was announced in September 1913, it had already been redefined to a straighter path between Lima and Galion; the rest of the straightening came later. The towns along the route got together and formed the Harding Highway, named after President Warren G. Harding, who had grown up in the area.
This Harding Highway continued east via the Lincoln Highway to Canton, turning southeast from there to Steubenville via State Route 43. To the west, it was marked along the Lincoln Highway to Van Wert, heading west along the present U.S. Route 224, roughly State Road 114, State Road 10, State Road 8, and State Road 2 through Indiana to the Illinois state line.
||This section contains a table that is missing mileposts for one or more junctions. Please help by .|
|Allen||Delphos||US 30 west – Van Wert, Fort Wayne||Western terminus of SR 309|
|SR 117 west||Western end of SR 117 concurrency|
|SR 65 north||Western end of SR 65 concurrency|
|SR 65 south||Eastern end of SR 65 concurrency|
|I‑75 – Cincinnati, Dayton, Toledo|
|SR 117 east||Eastern end of SR 117 concurrency|
|Hardin||Alger||SR 235 south||Eastern end of SR 235 concurrency|
|Ada||SR 235 north||Western end of SR 235 concurrency|
|SR 701 east||Western terminus SR 701|
|Kenton||US 68 / SR 67 – Bellefontaine, Findlay|
|SR 203 south||Northern terminus of SR 203|
|Marion||SR 95 west||Western end of SR 95 concurrency|
|SR 4 / SR 423|
|SR 95 east||Eastern end of SR 95 concurrency|
|SR 100 north||Southern terminus of SR 100|
|Morrow||SR 288 east||Western terminus of SR 288|
|SR 61 south||Southern end of SR 61 concurrency|
|Crawford||Galion||SR 19 west / SR 598 north||Western end of SR 19 concurrency; southern terminus of SR 598|
|SR 19 east||Eastern end of SR 19 concurrency|
|SR 61 north||Northern end of SR 61 concurrency|
|Richland||SR 181 west||Eastern terminus of SR 181|
|SR 430 east||Western terminus of SR 430|
|Mansfield||US 30 east – Mansfield, Wooster||Eastern terminus of SR 309|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi
- Ohio Department of Transportation. "Technical Services Straight Line Diagrams".
- "Renaming Of Rt. 30s Draws No Opposition". The Lima News. October 12, 1973. p. 13. Retrieved August 20, 2014.
- Butko, Brian (2013) . Greetings from the Lincoln Highway. Stackpole Books. p. 84. Retrieved August 20, 2014.
- Associated Press (September 20, 1973). "Eye U.S. 30 Location". The Times Bulletin. p. 1. Retrieved August 20, 2014.
- Map of Ohio Showing State Highway System (MrSID) (Map). Cartography by O.W. Merrell, Director. Ohio Department of Highways. 1932. Retrieved August 19, 2013.
- Map of Ohio Showing State Highway System (MrSID) (Map). Cartography by O.W. Merrell, Director. ODOH. 1934. Retrieved August 19, 2013.
- Official 1935 Ohio Highway Map (MrSID) (Map). Cartography by John Jaster, Jr., Director. ODOH. 1935. Retrieved August 19, 2013.
- Rand McNally Auto Road Atlas, 1926, accessed via the Broer Map Library