US 123 begins at a partial interchange with US 23, US 441, SR 15 and SR 365 east of Clarkesville. The interchange provides access between US 123 and those highways in the direction of Cornelia, Gainesville, and Atlanta. Access to northbound US 23, US 441, and SR 15 is provided via SR 17 (Toccoa Highway), which US 123 meets at its next intersection and with which the highway begins to run concurrently. US 123 and SR 17 head east along a four-lane divided highway through Chattahoochee National Forest. The highways cross the Habersham–Stephens county line and pass over Norfolk Southern Railway's Greenville District while passing along the north side of Currahee Mountain. At their intersection with SR 184 (Dicks Hill Parkway), SR 17 continues southeast along the divided highway toward Lavonia while US 123 turns north and joins SR 184 on Curahee Street, which forms the border of the national forest until the highways reach the city limits of Toccoa.