U.S. Route 231 in Kentucky

U.S. Route 231 (US 231) in Kentucky runs 114 mi from the Tennessee state line near Adolphus to the William H. Natcher Bridge on the Ohio River (Indiana state line) near Rockport, Indiana. It crosses the state mainly in the west-central region, traversing Allen, Warren, Butler, Ohio, and Daviess Counties.

Route description
Running concurrently with U.S. Route 31E for its first 8.607 mi in Kentucky, US 231/31E enters the state from Sumner County, Tennessee, and into Allen County. The two routes separate on the west side of Scottsville after the KY 100 junction. US 231 turns northwestward onto a four-lane highway on its way into Warren County, and into Bowling Green. Just before entering the city, US 231 crosses the southern terminus of KY 9007, a short connector providing access to I-65 and I-165. US 231 crosses I-65 in the Greenwood neighborhood of Bowling Green, US 31W and US 68 within city limits, and I-165 on the northwestern edge of the city.

US 231 reaches Butler County to cross I-165 for a second time, and runs concurrently with KY 79 on the southern end of Morgantown. On the northern end of Morgantown, KY 70 joins in on the concurrency as US 231, KY 79, and KY 70 cross the Green River. Both state routes separate from US 231 in the Aberdeen area before crossing the I-165 for a third time before entering Ohio County. US 231 meets U.S. Route 62 in the Beaver Dam/Hartford area after crossing the Wendell H. Ford Western Kentucky Parkway on the south side of Beaver Dam.

US 231 goes further north into Daviess County to join up with US 60 (Wendell H. Ford Expressway) to bypass Owensboro. US 60 splits from US 231 before leaving the state via the William H. Natcher Bridge going into Spencer County, Indiana.

Alternate names
U.S. 231 has several alternate names throughout its course in Kentucky. They include:
 * Scottsville Road (Allen/Warren County line to US 231 Bus/KY 880)
 * Campbell Lane (Bowling Green, from US 231 Bus/KY 880 to US 68/80)
 * Vietnam Veterans Boulevard (US 68/KY80 to US 231 Bus)
 * Morgantown Road (Warren County, US 231 Bus/US 68 to Butler-Warren County line)
 * Bowling Green Road (Butler County south of Morgantown)
 * South Main Street (Morgantown)
 * G.L. Smith Street (Morgantown)
 * Beaver Dam Road (Aberdeen to Butler-Ohio County line)
 * New Hartford Road (Daviess County, from Ohio County line to US 60)

Kentucky Route 71
In Kentucky, US 231 was originally signed as Kentucky Route 71, one of many charter routes of Kentucky's statewide system of highways when it was established in 1929. KY 71 originally ran from downtown Scottsville to downtown Owensboro. Prior to 1936, KY 71 followed the present-day KY 403 from Morgantown to Cromwell via Logansport and a ferry crossing. In 1936, KY 71 was rerouted to Aberdeen in order to accommodate the alignment KY 70 and KY 105 (now KY 79) via another ferry crossing between Morgantown and Aberdeen. A bridge over the Green River between the two cities opened around 1952, replacing the Morgantown-Aberdeen Ferry. In 1952, US 231 replaced the designation of KY 71 in its entirety as the U.S. route was extended from Montgomery, Alabama into Kentucky and Indiana via Huntsville, Alabama and Murfreesboro, Tennessee. US 231 also replaced parts of KY 75's course through downtown Owensboro, including its final stretch onto the Owensboro Bridge into Indiana. Kentucky Route 71 was reassigned as a renumbering of KY 231 from Jarvis Store to Bush, but this was later renumbered to KY 1803 because of I-71.

Modern-day realignments (1990-present)
In August 1999, US 231 in Bowling Green was rerouted onto KY 880 (Campbell Lane) from the Scottsville Road intersection to the Morgantown Road intersection on the northwest side of town. The former alignment of US 231 into downtown Bowling Green was redesignated as U.S. 231 Business.

In 2002, US 231 in Daviess County was rerouted from downtown Owensboro onto the then-new William H. Natcher Bridge north of Maceo. It previously followed the current KY 2155 and KY 2262 onto the Owensboro Bridge in downtown Owensboro into Spencer County until the opening of the Natcher Bridge.

Widening of Morgantown's South Main Street
The stretch of US 231 from the Natcher Parkway (now I-165) interchange to Bell Street in Morgantown was widened to include a center lane for left-turning in 2013–2014.

Scottsville Road speed limit increase
In late May 2017, the KYTC raised the speed limit of US 231 from near Scottsville to the near the Drakes Creek bridge south of Bowling Green from the original 55 mph to 65 mph. This makes this stretch of US 231 the second section of a four-lane divided highway with unlimited access in the region with a 65 mph speed limit, the first being US 68/KY 80 from I-24 in Trigg County to the Natcher Parkway Exit 7 (now I-165 Exit 5) interchange at Bowling Green.