The Oyster House in Olympia caught fire just after midnight.
Firefighters raced to the scene after an eyewitness called 911 and reported she could smell smoke coming from the building.
Crews say intense flames forced them to back out of the building after they arrived on scene at 12:45 a.m. Friday. They eventually declared a second alarm and called for backup to battle the raging blaze, as flames roared from the windows and roof.
According to the restaurant's website, the building was part of the original Olympia Oyster Co. formed prior to 1900.
The building's old age is one of the main reasons the fire took off so suddenly and fiercely.
"The old material makes for a very strong building, but once it catches on fire there's a lot of building to burn, and so there were heavy timbers that were on fire and heavy decking that held the fire in and allowed the fire to get very aggressive before we got here," says Greg Wright of the Olympia Fire Department.
Once the fire was extinguished, crews spent the rest of the night and early morning battling stubborn hot spots. One firefighter suffered a burn on the wrist.
The cause of the fire is under investigation.