Investigators say the cause of the fire is unknown.
The Den has had several different names over the last 40-years and managers say it is a real loss to the lesbian, gay, bisexual and transgender community.
Dave Smith said, "...safe place to hang out. Very enjoyable. Good atmosphere. It's going to be missed and a tough loss for lots of people."
Damage to the building is estimated at $130,000. The owners have not said if they plan to rebuild or relocate.
