The blaze also cut a power line and caused the Quillayute Valley School District to cancel classes, officials said.
The fire was reported before 4 a.m. in a three-story wooden facility known as the Oddfellows building. It was "fully involved," and the first firefighters who went inside knew the building couldn't be saved, said Phil Arbeiter, a Clallam County fire chief. Other firefighters then remained outside.
An explosion, possibly from a propane tank, spread the fire to an adjoining one-story building known as the Twilight store because of its merchandise. The business wasn't open.
The Quillayute Valley School District cancelled classes Monday at the elementary, middle and high school because of a cut power line. Arbeiter expected the line will be repaired in time for school to resume Tuesday.
The Oddfellows building housed a theater group and Hispanic grocery, Arbeiter said.
No one was in the buildings at the time. No firefighters were injured, and the cause of the fire remained under investigation.
A damage estimate wasn't immediately available. The city owned the Oddfellows building and it likely was insured, Arbeiter said. A bank owned the Twilight store.
The Olympic Peninsula town of Forks is about 100 miles west of Seattle near the coast.