US 25/421 also runs concurrently with I-75 between Exits 97 and 99. After Exit 99, the two U.S. routes continue to run concurrently until downtown Lexington just after crossing US 27/60/68. While US 25 makes a right turn onto Georgetown Road, US 421 continues straight northwestward, as Leestown Pike, towards Midway and Frankfort.[5]
Frankfort to Ohio River
In Frankfort, US 421 has concurrencies with US 60 on the east side of town, and US 127 on the north side. US 421 continues northwestward into Henry and far northern Shelby counties before crossing the Exit 34 exit of I-71. US 42 in Bedford is the last major intersection in Kentucky before US 421 crosses the Ohio River from Trimble County into Jefferson County, Indiana.[6]
US 421 did not have any presence in Kentucky until it was extended into Kentucky and Indiana at one point between 1939 and 1957, probably in the late 1940s or early 1950s.[7] When US 421 was designated into Kentucky, it was routed onto the following existing routes:
The remainders of KY 21, KY 169, and KY 257 still retained their original alignments off the current US 421.
KY 50 no longer exists in the state route system.
KY 66 is now assigned to a road in Bell, western Leslie and eastern Clay Counties in southeast Kentucky from Middlesboro to US 421/KY 80 near Big Creek