{{Short description|State highway in northeastern Ohio, US}} {{Use American English|date=May 2025}} {{Use mdy dates|date=January 2025}} {{Infobox road |state=OH |type=SR |route=166 |map=OH 166 map.svg |maint=ODOT |length_mi=11.40 |length_round=2 |length_ref=<ref name="sld">{{cite web |url=http://www.dot.state.oh.us/Divisions/Planning/TechServ/TIM/Pages/Straight-Line-Diagrams.aspx |title=Technical Services Straight Line Diagrams |author=Ohio Department of Transportation |author-link=Ohio Department of Transportation |accessdate=2006-11-12}}</ref> |established=1923<ref name=ODOT1922_map /><ref name=ODOT1923_map /> |direction_a=West |terminus_a={{jct|state=OH|US|6}} near Chardon |junction= |direction_b=East |terminus_b={{jct|state=OH|OH|534|CR|12|county2=Ashtabula}} near Rock Creek |counties=Geauga, Ashtabula |previous_type=SR |previous_route=165 |next_type=SR |next_route=167 }}
'''State Route 166''' ('''SR 166''') is an east–west state highway in the northeastern portion of the U.S. state of Ohio. The western terminus of State Route 166 is at a T-intersection with U.S. Route 6 just over {{convert|3|mi|km}} northeast of Chardon. Its eastern terminus is at State Route 534 about {{convert|5|mi|km}} west of Rock Creek.
==Route description== State Route 166 starts in Hambden, traveling northeast through the northwest corner of Montville Township, passing by Curtis Airport. After it crosses into Thompson Township, it curves to face the east. It then crosses the county line into Ashtabula County, ending at SR 534, near Rock Creek. No segment of this highway is a part of the National Highway System, a system of highways identified as most important for the economy, mobility and defense of the nation.<ref name="NHS">{{cite map | title=National Highway System: Ohio | date=December 2003 | publisher=Federal Highway Administration | url=http://www.fhwa.dot.gov/planning/nhs/maps/oh/oh_Ohio.pdf | archive-url=https://web.archive.org/web/20081016165827/http://www.fhwa.dot.gov/planning/nhs/maps/oh/oh_Ohio.pdf | url-status=dead | archive-date=October 16, 2008 | format=PDF|accessdate=2011-01-08}}</ref>
==History== The debut of State Route 166 took place in 1923. The original routing of State Route 166 consisted of the existing route of State Route 166 from its current western terminus northeast of Chardon to its junction with State Route 528, and State Route 528 from that intersection north to that highway's current northern terminus north of Madison.<ref name=ODOT1922_map>{{cite map |title=Map of Ohio State Highways |url=http://www.dot.state.oh.us/Divisions/TransSysDev/Innovation/prod_services/Documents/StateMaps/otm1922a.sid |format=MrSID |publisher=Ohio Department of Highways and Public Works |date=April 1922 |cartography=ODHPW |accessdate=2011-01-08}}</ref> <ref name=ODOT1923_map>{{cite map |title=Map of Ohio Showing State Routes |url=http://www.dot.state.oh.us/Divisions/TransSysDev/Innovation/prod_services/Documents/StateMaps/otm1923a.sid |format=MrSID |publisher=Ohio Department of Highways and Public Works |date=July 1923 |cartography=ODHPW |accessdate=2011-01-08}}</ref> In 1939, State Route 166 was re-routed. From the current junction of State Route 166 and State Route 528, State Route 166 was routed east, replacing what was formerly designated as State Route 522, to the intersection that marks State Route 166's current eastern terminus at State Route 534 west of Rock Creek. In turn, State Route 528 was extended northward, replacing what was the north-south leg of State Route 166.<ref name=ODOT1939_map>{{cite map |title=Ohio Highway Map |url=http://www.dot.state.oh.us/Divisions/TransSysDev/Innovation/prod_services/Documents/StateMaps/otm1939a.sid |format=MrSID |publisher=Ohio Department of Highways |date=1939 |cartography=ODOH |accessdate=2011-01-08}}</ref> <ref name=ODOT1940_map>{{cite map |title=Ohio Highway Map |url=http://www.dot.state.oh.us/Divisions/TransSysDev/Innovation/prod_services/Documents/StateMaps/otm1940a.sid |format=MrSID |publisher=Ohio Department of Highways |date=1940 |cartography=ODOH |accessdate=2011-01-08}}</ref>
==Major intersections== {{OHinttop|length_ref=<ref name="sld"/>}} {{OHint |county=Geauga |cspan=3 |ctdab=Geauga |location=Hambden Township |mile=0.00 |road={{jct|state=OH|US|6}} |notes= }} {{OHint |ctdab=Geauga |location=Thompson Township |lspan=2 |mile=4.09 |road={{jct|state=OH|OH|86|name1=Plank Road}} |notes= }} {{OHint |mile=6.59 |road={{jct|state=OH|OH|528|city1=Thompson Township, Geauga County|city2=Middlefield|name1=Madison Road}} |notes= }} {{OHint |county=Ashtabula |ctdab=Ashtabula |location=Trumbull Township |mile=11.40 |road={{jct|state=OH|OH|534|CR|12|county2=Ashtabula|name2=Footville-Richmond Road|city1=Geneva|city2=Windsor}} |notes= }} {{Jctbtm}}
==References== {{Reflist}}
==External links== {{Attached KML|display=title,inline}} *[https://web.archive.org/web/20061117222525/http://www.state-ends.com/ohio/oh166/ State Route 166 Endpoint Photos]
166 Category:Transportation in Geauga County, Ohio Category:Transportation in Ashtabula County, Ohio