Complex sentence: US 460 replaced the entire route west of Paintsville in the 1940s, but in about 1980 it was moved onto a new alignment east of Salyersville, and KY 40 was extended back west.
Split into simpler sentences: US 460 replaced the entire route west of Paintsville in the 1940s. Around 1980, it was moved onto a new alignment east of Salyersville, and KY 40 was extended back west.