I think this is one of those questions on which everyone can claim to be correct and the differences in answers attributed to equally valid interpretations.
Without question the Seaboard’s lines lead away from the diamond at the passenger station north, south, east and west.
But as Bruce points out, a train heading east out of town comes to a switch within a few hundred yards after passing over Highway 38. If the train takes the left fork, it continues east toward Pembroke, where it crosses the old Atlantic Coast Line mainline, and on to its terminus at Wilmington. If the train takes the right fork, it curves to the south, crosses the ACL mainline at Dillon, S.C., and passes through Georgetown, S.C., and Charleston, S.C., on its way to joining the Seaboard’s north-south mainline at Savannah, Ga.
It does, as Lynn says, branch off the eastbound main, but in the larger scheme of the Seaboard’s route system it served as a parallel alternate route for north-south trains between Hamlet and Savannah.
As you can see from the map above showing five lines radiating from the hub in Hamlet, the line from Hamlet to Savannah through Charleston is somewhat longer than the line through Columbia, S.C. But because it’s located farther east, it runs across flatter ground with fewer curves and was an easier and cheaper route for freight trains, because it took less power to pull the weight. Less coal burned and smaller locomotives in the steam era, fewer diesels for a train in the modern era. The route through Columbia was shorter and faster for passenger trains, which are lighter than freights.
For the railroad it was all about engineering and economics. For this discussion, the Charleston line was a line that branched from the eastbound main – a fifth line – but whose purpose was to carry north-south traffic, a purpose it shared with another line.