Construction and relocation of KY 80 in Graves, Calloway, and Marshall counties during this time caused the route to be split.

The route is now a four-lane divided highway from Mayfield to Bowling Green after the widening to four lanes from Canton to Cadiz was completed in 2020.

[citation needed] From Columbus, the road passes through Hickman, Carlisle, and Graves counties to Mayfield.

From Glasgow to Somerset, KY 80 is paralleled (and largely supplanted) by the Louie B. Nunn Cumberland Parkway, which is officially designated as the future route of Interstate 66 (I-66), although interest in that project has been lost.

KY 80 serves rural portions of Clay, Leslie, and Perry counties, including the city of Manchester, before rejoining the Parkway near Hazard.

[2] In the late 1940s, when US 68 was rerouted to its current routing between Bowling Green and Perryville, KY 80's western terminus was truncated to its junction with US 68 in Edmonton.

[3] Dyche, who also led a motorcade to KY 80's current western terminus all the way from Elkhorn City, continued to promote the highway until his late 1959 death.

[6][7] The state's I-66 proposals called for KY 80 to be bypassed in the area between Somerset and London, with the new road to share only the crossing over the Rockcastle River gorge.

[8] This proposal has met with controversy in the mid-2000s, with area residents preferring that the new Interstate be built on the existing KY 80 right of way.

Old alignments of US 68/KY 80 in Fairview, Elkton, Russellville, Auburn, Bowling Green and Glasgow were converted into business routes of US 68.

[10] Around that time, KY 80 was re-routed onto a four-lane highway from Mayfield to Aurora via the northern outskirts of Murray.

Previously, KY 80 had 2.199-mile (3.539 km) gap within the city from the Purchase Parkway (now-Interstate 69) interchange to US 45 in downtown Mayfield.