 In Lowndes County, SR 21 begins its first concurrency with US 80, and the two highways enter Montgomery, the state capital, from the southwest.SR 21 then diverges northeastward from US 80 for a short concurrency with US 31, then travels concurrently with US 80 once again (as well as US 82) around the Montgomery city center, diverging from US 82 at US 231 and traveling concurrently with US 231 northward to Sylacauga at an interchange with US 280.From Sylacauga, SR 21 turns northeastward toward Talladega.