SC 125 is predominantly a two-lane rural highway, traveling in a northwesterly direction for. Beginning in downtown Allendale, it is also known as the Augusta Highway and travels northeast to Martin before entering Barnwell County. Soon after entering Barnwell County is the Savannah River Site, which is limited to through traffic only. After a drive, and well into Aiken County, travelers exit the Savannah River Site and enter the town of Jackson. Continuing north, on what is now called Atomic Road, SC 125 joins a concurrency with US 278 from Beech Island to Clearwater. Entering North Augusta, it crosses Interstate 520 without an interchange and connects with US 25 before the road ends at Buena Vista Avenue. Going west on Buena Vista Avenue, it meets US 25 Business at Georgia Avenue where it ends, from Augusta.
Savannah River Site
SC 125 is the only highway through which the public is allowed to travel through the Savannah River Site. However for the stretch it travels through SRS, vehicles are prohibited from stopping except for emergencies. Mile-markers going north to south help travelers count the miles before they are out of the restricted area. The highway is flanked with trees and fences and, on occasion, defunct roads crossing the highway with gates restricting access; the biggest being the former SC 64 interchange near mile marker 8. Though the highway is maintained by SCDOT, it is patrolled by federal security; the speed limit throughout is. Prior to 2006, checkpoints were located at both ends of SC 125. When arriving at the entrance checkpoint, drivers would receive a pass and may also have their car searched at that time. Drivers were required to return the pass at the exit checkpoint; for those that drove too quickly to the other end would be issued a speeding ticket. Drivers that failed to either return the pass or arrive later than expected could be withheld for further questioning by authorities. After 2006, the checkpoints were removed along route, though checkpoints still exist at some roads that go deeper into the Savannah River Site.
History
The highway was originally established around 1938 as a new primary routing from US 1/US 78 in Hamburg to US 25 in North Augusta. In 1953, SC 125 was rerouted onto Atomic Road and extended south along new four-lane primary routing to Beech Island, connecting with SC 28; then continuing south, through Jackson, to the Savannah River Site, ending at the gate. In 1965, US 278 was overlapped between Clearwater to Beech Island. Between 1968-1970, SC 125 was extended southeast again through the Savannah River Site, ending at its current southern terminus in Allendale; SC 125 replaced what was SC 28 prior to 1951 and replaced part of SC 641, north of Allendale.
SC 125 truck route travels north along Martintown Road, in concurrency with SC 230, then south on Georgia Avenue, in concurrency with US 25 Business, ending at the northern terminus of SC 125 at Buena Vista Avenue. The truck route stays along the commercial corridors of North Augusta, avoiding the homes and a park that exist along SC 125.
