As it leaves the Columbia area, I-77 has a diamond interchange with Killian Road and a partial cloverleaf interchange with US 21 (Wilson Boulevard). North of its diamond interchange with Blythewood Road in Blythewood, the highway enters Fairfield County. I-77 meets SC 34 west of the town of Ridgeway and passes under the NS R-Line. The freeway passes to the east of Winnsboro, which is accessed via SC 34 or the next interchange with Road 41. I-77 has junction with Road 20 and SC 200 near Mitford before entering Chester County. The freeway has an interchange with SC 97 (Great Falls Road), which connects the county seat of Chester to the west with the town of Great Falls to the east. Great Falls is where the Piedmont-based Catawba River reaches the fall line and becomes the Wateree River of the Atlantic Coastal Plain.
At Richburg, I-77 has interchanges with Road 56 and SC 9 (Lancaster Highway) just before the freeway enters York County. The highway has interchanges with SC 901 (Mount Holly Road) and Porter Road on the southeast side of Rock Hill. I-77 expands to eight lanes at its partial cloverleaf interchange with US 21 and SC 5 (Anderson Road) and enters the city of Rock Hill. The freeway has a diamond interchange with SC 122 (Dave Lyle Boulevard) west of the Rock Hill Galleria. North of its underpass of the Columbia District rail line, I-77 has a pair of connected partial cloverleaf interchanges with US 21 (Cherry Road) and SC 161 (Celanese Road). The Interstate then leaves the city of Rock Hall by crossing the Catawba River.
I-77 has interchanges with Sutton Road and SC 160 (Steele Creek Road) as it passes along the western edge of Fort Mill. North of Fort Mill, the Interstate has a diamond interchange with SC 460 (Gold Hill Road). SC 460 provides access to Knights Stadium, home of the Charlotte Knights of minor league baseball. I-77's final interchange in South Carolina is with Carowinds Boulevard, which provides access to the Carowinds theme park immediately to the west on the South Carolina–North Carolina state line. At the partial cloverleaf interchange, US 21 begins to run concurrently with I-77; the two highways cross the state line together into the city of Charlotte.
