Co-owner Tom Walls says he's been trying to negotiate a new lease with the property's owner since December, but he received an eviction notice on Wednesday.
"If you don't own the building," he said, "you don't control your destiny. So, we couldn't work out a lease, and she wants the space."
The Diner closed its doors at 4 p.m. Sunday, and many patrons and former employees showed up to say goodbye.
"We were just talking earlier that it's kinda our Cheers," former waitress Dara Pechan said. "You know, you come in, the bartenders know you, the servers know you."
Not only did the restaurant help pay for Pechan's college tuition, it introduced her to Sean Pechan, her husband.
"We are now married with two great kids," she said, "and this was the place we came after we got engaged."
Walls said he hopes to find another location and someday open a new Rocky Mountain Diner.
"It's a sad day," Walls said, "But, you know, we've had a great run."
(KUSA-TV © 2011 Multimedia Holdings Corporation)