They curve to the west again, traveling through the town of Jenkinsburg, then enter Henry County. The two routes curve again to the north-northwest and pass through Locust Grove. Then, they enter McDonough, where they intersect SR 155 (North McDonough Road) and then SR 20/SR 81. They pass by Alexander Park before crossing over Camp Creek and leaving town. Then, US 23/SR 42 enter Stockbridge. There, they pass Eagle's Landing Parkway and then head west-northwest on a concurrency with SR 138. The three routes curve to the northwest and reach the end of the concurrency. US 23/SR 42 resume their north-northwest routing and enter Clayton County. The two routes have an interchange with I-675 and then travel through the town of Rex. They skirt along the eastern edge of Fort Gillem and pass by Conley Park, just before entering DeKalb County. US 23/SR 42 meet the northern terminus of SR 54 Conn. (Thurman Road) before an interchange with I-285. They pass to the east of the Lake Charlotte Nature Preserve. After that, they cross over the South River, enter Atlanta, and run along the Fulton–DeKalb county line. They pass by Chestnut Hill Cemetery and meet the eastern terminus of SR 42 Spur (McDonough Boulevard SE). Then, they pass by the western side of Brownwood Park before meeting the western terminus of SR 260 (Glenwood Avenue SE). Just over later is an interchange with I-20. Immediately north of there is SR 154 (Memorial Drive). The two highways travel through the Little Five Points district of the city. They travel through a portion of Freedom Park and meet the eastern terminus of SR 42 Conn. (Freedom Parkway). Just over later, they intersect US 29/US 78/US 278/SR 8/SR 10 (Ponce de Leon Avenue). At this intersection, US 23 splits off to the east, while SR 42 continues to the north. Almost immediately afterward, it curves to the northeast, re-entering DeKalb County proper. Then, it heads fairly northward, passing between Emory University and Herbert Taylor Park and crosses over South Peachtree Creek. It intersects SR 236 (Lavista Road NE). Then, SR 42 turns to the left onto North Druid Hills Road NE.