The fire began around 7 p.m. PT and witnesses say about a third of the bridge over the Columbia River was in flames.
There was no train on the bridge at the time.
Debbie Ife lives just across the way from the bridge.
"The smoke was just black and billowing. We had a breeze that happened to be blowing it down the river," she said.
The cause of the fire and the extent of the damage is still unknown, a Canadian Pacific Railway spokesperson said.
Officials expect to reopen the bridge Sunday, but said they don't yet know what time that will happen.