After a few tenths of a mile KY 12 turns back toward the east and enters Franklin County where it becomes more narrow and curvy.

3.405 miles (5.480 km) from the Shelby County line, KY 12 forms a junction with US 421.

The portion of this road that traveled from KY 43 to the community of Bagdad had a graded, hard surface, the portion traveling from Bagdad to the Franklin County line was gravel surfaced, while the rest of the highway was unimproved.

[2] Between 1939 and 1941, the rest of present-day Route 12 was created as a graded, unpaved road, but was not yet designated as part of the highway.

[4] From 1942 to 1955, the portion of highway in Shelby County underwent minor rerouted, with an overall length of 6.8 miles (10.9 km).