SR 271 was a state highway through east-central Ohio. When it was first designated in 1932, it ran from Coshocton to North Salem taking over a part of SR 95. In 1935, the route was vastly expanded west to include all of the former SR 309 from Tunnel Hill to Coshocton, unnumbered roads from New Guilford to Tunnel Hill, and part of SR 206 from Martinsburg to New Guilford. The route experienced one more extension, this time at its eastern terminus to act as a spur to the community of Birmingham. No major changes would occur to SR 271 until 1962 when the route was renumbered to SR 541 due to the new Interstate highway, I-271.
SR 272 was a 1.2-mile-long (1.9 km) state highway located north of downtown Canton. The entire route followed Canton's 30th Street and connected SR 8 and US 62/SR 43. The route was in existence from 1930 until 1961, though for its last year as a state route, SR 272 was marked on the official Ohio highway map. After 1961, US 62 was brought onto a new freeway alignment just south of 30th Street. SR 272 was deleted from the system as a result.
SR 275 was a state route stretching from Rosewood to just west of Marysville. The first section of SR 275 that was designated was its segment from West Liberty to Marysville at SR 32 (later US 33); it was signed in 1930. In 1937, the route was extended west to SR 29 near Rosewood. After 1962, the SR 275 designation was replaced by SR 245 due to the signing of I-275 near Cincinnati.
SR 277 was the predecessor to SR 207 and ran from north of Chillicothe at SR 104 to Mount Sterling. The route when it was created in 1930 originally had its northern terminus at US 22 in Atlanta. The route was extended to its long-time northern terminus in 1935. No major changes would occur to the route until the route was renumbered to SR 207 in 1962 due to the construction of I-277 in Akron.
SR 280 was a state highway that existed from 1930 until 1962 and traveled between Amesville and Trimble. The route remained along this alignment for its entire 32-year history. In 1962, due to the building of I-280 in the Toledo area, all of SR 280 became part of an extension of SR 329 which previously ended at US 50 Alt. in nearby Bern Township.
SR 283 was a short-lived designation for a 1.2-mile-long (1.9 km) state route near Holland. This designation had replaced SR 223 which had to be renumbered due to the addition of US 223 in the state. Within one year, the route number was changed again, this time to SR 326.
SR 288 was the predecessor to SR 640 in Lake County. The route was designated in 1931 on the Willowick–Willoughby route it followed for its entire history. In 1940 for unknown reasons, the route number was changed to SR 640.
SR 289 was a short state route entirely in New Haven Township. The route existed from 1931 until 1937 and acted as a connector from SR 61 to the former SR 194. After 1937, the entire route became the northernmost 1.18 miles (1.90 km) of SR 598 following its extension to Huron County.
SR 290 was the state route that became SR 296 in 1962. The route throughout most of its history consisted of a routing starting north of Urbana and traveling east to the community of Middletown within Wayne Township, Champaign County. According to the 1932 official Ohio state highway map, SR 290 traveled along the former SR 275 between West Liberty and Middletown even though prior and successive maps show this segment as SR 275. By 1933, SR 290 was routed from US 68 near Kings Creek to SR 275 in Middletown. In 1937, the route was extended slightly west to end at SR 29 (originally SR 54). After 1962 when Ohio routes that shared numbers with proposed Interstate highways were renumbered, SR 290 became SR 296 because of the proposed Interstate 290 in Cleveland (which later was built as I-490).
SR 291 was a two-mile-long (3.2 km) alternate state route to SR 69 in Liberty Township, Hardin County. While SR 69 shared a one-mile-long (1.6 km) concurrency with US 30S east before turning north, SR 291 continued north from the western SR 69/US 30S intersection before making a 90-degree turn to the east. The route was in existence from 1932 until 1945.
SR 296 was a state route that connected SR 4 on the Seneca–Huron County line to the village of Bellevue. The route, which was about seven miles (11 km) long, followed the county line for its entire length. The route was created in 1932 and was replaced in 1936 by an extended SR 269.
SR 297 was a short spur route that connected the village of Wayne to US 6 near Bradner. The route, which had been asphalt-paved for its entire history, was created in 1932 and existed until 1938 when it was absorbed into a lengthened SR 281, the number the road still carries today.
SR 298 was a state road that connected SR 4 north of Chatfield to Willard at US 224 and SR 194. The route when it was created in 1932 only consisted of the segment from its western terminus at SR 4 to the village of New Washington. In 1938, the route was extended east and north through Gardner and Celeryville to end at US 224 and SR 194 near Willard. The route would follow this alignment until after 1967 when all of SR 298 and SR 194 was replaced by SR 103 which had been extended from its former end in Chatfield.
SR 299 was a state route that traveled from Milan to Huron. The route's southern terminus was at US 250 and SR 13 just north of Milan and its northern terminus was at US 6 and SR 2 in downtown Huron. The route maintained this routing throughout its history. Prior to 1966, SR 13 followed US 250 into Sandusky but in 1966, SR 13 was rerouted to follow the entire length of SR 299 thus deleting this number from the system.
SR 309 was a state route that ran from the community of Tunnel Hill to the now-defunct village of Roscoe. During its two years of existence from 1932 until 1934, the route was entirely a gravel road. After 1934, SR 309 became one of many state routes and local roads that became a part of a greatly extended SR 271 that stretched from Martinsburg to North Salem. Today, all of the former SR 309 is a part of SR 541.
SR 311 was a short spur state route from the village of Brookville to the community of Arlington (within Clay Township) at US 40. This alignment of the route would be its route throughout its entire history from 1932 until 1964. As I-70 was built through the area in the early 1960s, the state route was removed from the system though it did feature an interchange with the new Interstate. Today, the portion of the former state route outside of the village limits is a part of Montgomery County Road 6.
SR 326 was the final designation for a 1.2-mile-long (1.9 km) state route near Holland. The route had been renumbered from SR 283 in 1932 but after 1934, the route was removed from the state highway system altogether.
SR 326 was a short state route in and around Marietta, Washington County. The route became a state road in 1935 but was unlabeled on Ohio state highway maps until 1946. The route began in downtown Marietta as Washington Street before heading into the hills north of the downtown as Cisler Drive and ending at SR 375. The route would be in existence along this routing until after 1967 when it was reverted to local control.
SR 333 was a state route in the vicinity of Sylvania. The route started in the Central Avenue Park neighborhood of Sylvania Township at US 20 and SR 120 and traveled north on North Holland Sylvania Road. SR 333 curved to the northwest as it entered the city limits of Sylvania. In downtown Sylvania, the route ended at the intersection of Main and Monroe Streets. US 223 traveled east and north of this point. The route was created in 1946 when SR 120 was rerouted from this road onto a more southerly alignment. SR 333 would be deleted by 1964 having been replaced by new freeways, US 23 as the predominantly north-south bypass of the route and I-475 serving as another alternate route.
SR 336 was a state route in northwestern Ohio and existed from 1932 until 1945. At the time of its creation, the entire length of SR 336 was a former section of US 127. In that year, US 127 was moved onto an alignment closer to the Maumee River (including a concurrency with US 24) leaving SR 336 on the former segment. The route started at US 127 east of Cecil and traveled east before sharply turning to the north at the community of Emmet. SR 336 ended at the intersection which was also the eastern end of the US 127 / US 24 concurrency. After 1945, the entire route was deleted from the state highway system.
SR 338 was a state highway along the banks of the Ohio River in southeastern Meigs County. In 1932, the route was created as a spur from Letart Falls to SR 124 near Rolandus. By 1937, the route extended from Racine to SR 124 south of Portland. The route would follow this 21.7-mile-long (34.9 km) alignment for over sixty years until a truncation in 2003 left it at a length of 2.32 miles (3.73 km) from the Ravenswood Bridge to SR 124 south of Portland. The route was deleted between 2008 and 2012 and today, most of the route was abandoned due to landslides into the river.
SR 341 was a short state route near Beach City. The two-mile-long (3.2 km) highway was a connector from SR 212 east of Beach City to US 21. The route existed from 1933 until 1941 and was not replaced by another state route.
SR 346 was a state route in eastern Ohio that became a part of the Appalachian Highway in the 1970s. When it was created in 1935, SR 346 ran from SR 160 in Radcliff to SR 143 in Mount Blanco. The route would be on this alignment for 35 years until 1970 when the Appalachian Highway was opened through southern Ohio. The route was extended to a length of 20.8 miles (33.5 km) running from SR 124 south of Wellston to US 50 southwest of Albany. After 1983, the entire Appalachian Highway was assigned SR 32 therefore the SR 346 was deleted from this section of the divided highway.
SR 351 was a bypass of Marietta in Washington County. The route existed from 1935 until 1969. The route started in the eastern Marietta suburb of Norwood at US 50 Alternate and SR 7 (Pike Street) and headed north on Acme Street. At its intersection with SR 26 (Greene Street), SR 351 had a two-block concurrency west along SR 26 before turning right onto Colegate Drive. The route curved around the northeastern limits of Marietta intersecting SR 375 along the way. SR 351 ended at an intersection with SR 60 (Muskingum Drive) at the Muskingum River.