Tensions have been steadily escalating this week between the United States and North Korea.

It's been a war of words between the two leaders. North Korea issued a specific threat this week of test-firing ballistic missiles into waters off the U.S. pacific territory of Guam.

Japan began moving its missile defense system on Friday after that threat.

The nuclear war threat is something one local historian has studied in the past, post-World War II era.

Videos produced by the federal government in the 1950s suggested when and how to protect yourself from a nuclear explosion.

It's a piece of history Hamilton County Historian Linda Mines remembers well during the Cold War. She said fallout shelters were common in cities like Chattanooga.

"Some place below ground that was considered to be deep enough, walls were thick enough that in the event of something happening of that sort of disastrous level, that everybody would file to the basement and you'd be safe there," Linda Mines, Hamilton County's historian said.

At one time, Chattanooga Public Library records show there was a list of fallout shelters. 

One was inside UTC's Fletcher Hall that was once the city's public library. A symbol letting people know about the building's history is no longer there.

"We've assumed that the need for something of that nature sort of went the way of the Cold War," Mines said.

Now that tensions are rising between the U.S. and North Korea, some are wondering if fallout shelters will become relevant again.

"It's a bit unnerving to think about it resurrecting its head again," Mines said.

Mines said she hasn't heard of any serious conversations about the use of shelters in decades. She hopes it continues to be a war of words and nothing else.

"I think whether it becomes historical or not depends on what happens as we look forward," Mines said.

Historical documents show there were many fallout shelters in Chattanooga.

Memorial Auditorium, the old Newton Chevrolet dealership and Central High School are on the list.