Lewis County sheriff's deputies initially responded to the scene, in the 100 block of Hart Road in Winlock, on Monday evening after receiving a call from the owner, said Chief Deputy Stacy Brown.
The owner told deputies he was cleaning out the barn when he stumbled across the explosives, which were there before he bought the property and apparently had been in the barn for several decades.
Deputies called the Washington State Patrol Bomb Squad, which determined there were several extremely deteriorated and volatile explosives in the dilapidated and abandoned barn.
It was determined that the safest way to dispose of the explosives was to conduct a controlled burn of the barn.
Just before noon Tuesday, the Winlock Fire Department conducted the controlled burn without any issues. The building was almost entirely gone within minutes.
"Even though access to explosives is very limited to the average person this day and age, we continue to get calls about explosives being found or abandoned on property in our community," said Lewis County Sheriff Steve Mansfield.
"I continue to urge people not to pick up, handle, or transport anything that even remotely resembles an explosive device. The best thing to do is immediately leave the area and call our office."