U.S. Route 23 in Ohio

The route crosses over the Ohio River via the U.S. Grant Bridge into the city of Portsmouth. Through downtown Portsmouth, it follows parallel one-way streets; northbound traffic is on Gay Street and southbound on Chillicothe Street. These roads merge into Scioto Trail, which becomes a divided highway north of Rosemount, and again north of Lucasville, through Piketon to just south of Waverly.[2]

Within Waverly, the route runs concurrently with State Route 104 (SR 104), in addition to a four-block concurrency with SR 335 that ends in downtown Waverly. The concurrency with SR 104 ends just south of Chillicothe at which point US 23 becomes an expressway.[2] The route bypasses Chillicothe to the east, including a short concurrency with US 35 before once again becoming a divided highway near Kingston. It continues as such through Circleville to the southern edge of Columbus, at the southern junction of Interstate 270 (I-270).[2]

Columbus

Protected bike lane and bus stop island on Summit Street near the Ohio State University campus

In downtown Columbus, the route is applied to a one-way pair. It first jogs easterly via Livingston Avenue (north) and Fulton Street (south) before continuing northerly with northbound traffic on Fourth Street and southbound traffic on Third Street, which becomes Summit Street north of Fifth Avenue. The one-way pair ends at Hudson Street on the border of the SoHud and Glen Echo neighborhoods; both directions of US 23 jog westerly onto Hudson Street before continuing northerly on Indianola Avenue, closely paralleling I-71. The route then moves westerly again via Morse Road, then north again onto High Street on the north edge of the East Beechwold neighborhood. North of the northern junction with I-270, High Street becomes Columbus Pike.

The section immediately north of the northern junction with I-270 was upgraded with a northbound-only set of express lanes which passes under Dimension Drive, Campus View Boulevard, Radio City Boulevard, and Flint Road, with the former alignment of US 23 providing access to those roads. This configuration, known as the "Trench", opened to traffic in September 2015, and its construction coincides with a reconfiguration of the I-270 exit.[3] After the Trench, US 23 leaves Columbus heading north.

Before the establishment of the U.S. Numbered Highway System in 1926, the route of what would eventually become US 23 was numbered as SR 4 from Portsmouth to Marion; SR 22 from Marion to Carey; SR 63 from Carey to Fostoria; SR 199 from Fostoria to Millbury; and SR 2 from Millbury to Toledo.[4][5] Over the years, portions of US 23 have been realigned to divided highway, freeway, or expressway portions. Among these are a bypass of Circleville built in 1958;[6] the Marion–Carey expressway routing, on which work began in 1962;[7] and a bypass of Chillicothe, on which work began in 1966.[8]

When first established, US 23 followed its current routing from Fostoria to Woodville, then continued north along present-day Fostoria Road into Millbury and northwest along present-day SR 51 (Woodville Road) into East Toledo. There, it followed East Broadway Avenue, Starr Avenue, and Main Street to the Cherry Street Bridge (now the Martin Luther King Bridge) across the Maumee River. The route then followed Cherry Street (present-day SR 120) to Detroit Avenue (US 24), before turning west onto Laskey Road and north onto Lewis Avenue.[5] Only a year later, the Fostoria–Toledo routing was shifted westerly, taking a northwest–southeast route that was originally designated SR 63 between Fostoria and Perrysburg, then East River Road into Toledo. It crossed the Maumee River via the Fassett Street Bridge, then followed South, Sumner, Logan, Summit, and Huron streets to rejoin its original routing. The Fostoria–Millbury routing was designated SR 199, and the Millbury–Toledo routing became SR 102,[9] which in turn became present-day SR 51 in 1955.[10] By 1940, US 23 was shifted westerly again in Toledo, taking the Anthony Wayne Bridge to Summit Street, then to Jefferson Avenue and Collingwood Boulevard before rejoining the previous routing.[11]

US 23 was realigned c. 1960 to follow Monroe Street northwesterly out of Toledo, joining with the first constructed segment of its current freeway routing in Sylvania.[12][13] The freeway was extended southerly to US 20 (Central Avenue) by 1964.[14] By 1969, the entire western freeway bypass of Toledo was complete, carrying the current routings of both US 23 and I-475. In addition, US 23 and SR 199 were swapped north of Fostoria in 1969, as US 23 reverted to its pre-1927 routing between Fostoria and Woodville, then running concurrently with US 20 from there to Perrysburg. The 1927–1969 routing of US 23 between Fostoria and Perrysburg thus became part of SR 199.[15]

A plan was proposed by the Ohio Department of Transportation (ODOT) in July 2020 to improve safety along US 23 in Wyandot County by reconfiguring several intersections and closing others to eliminate cross traffic and turns across opposing traffic for the stretch of US 23 between the interchange at SR 231 in Marion County and the interchange at SR 199 south of Upper Sandusky.[16][17][18] After public comments, the proposal was revised to drop one intersection from the plan over concerns about the impact on emergency services. The rest of the plan was rejected by the Wyandot County Commission in May 2021 because of the impacts on the community and the community's preference for an interchange at SR 294.[19][20][21]

Weigh stations were once located on US 23 just north of the split with US 35, but they were decommissioned and later converted into truck parking in 2023.[22] Ross County had wanted the space to be utilized into a full interchange with Marietta and Seney Roads as a part of their 2008 Thoroughfare Plan.[23]

North of Upper Sandusky in Salem Township, Wyandot County, there have been a number of serious crashes at the intersection with County Road 44 and Township Road 44 from 2016 to 2021. To improve its safety, beginning April 11, 2022, ODOT will convert the intersection to a pair of right-in/right-outs and close the median crossover. Once this conversion is completed, the stretch of US 23 from SR 199 south of Upper Sandusky, through this junction, will be free of cross traffic and turns across opposing traffic.[24][25]