The collision occurred around 12:30 p.m. in the southbound lane near the 177 mile marker, Gaston Fire and Rescue Chief Ed Porter Jr. said in a statement.
A spokesperson for the state Highway Patrol, which is investigating the collision, could not immediately be reached for comment this evening.
Both southbound lanes were blocked by the fallen message board. The rig was found in the median.
Approximately 50 gallons of engine oil and diesel fuel were found leaking from the vehicle into a creek.
Firefighters used shovels and hand tools to create dikes to stop the fluids from spreading downstream.
The driver of the tractor-trailer was treated on scene by firefighters and paramedics. He was later transported by Northampton County EMS to Halifax Regional Medical Center in stable condition.
Both southbound lanes remained closed for approximately an hour and a half until the message board was safely removed from the highway.
Using chainsaws, firefighters removed the trees surrounding the rig so it could be towed.
The highway was reopened to one lane of travel until fire units cleared the scene around 3 p.m.