BOISE, Idaho — The Old Idaho Penitentiary opened its iron doors for some of the West's worst prisoners in 1872 and remained in use until 1973. In the hundreds of years it was open, the sandstone walls of the prison have a dark past and tales for tour members to learn more about.

Amber Bierle, a historic sites administrator for the penitentiary, said the tours are an annual event and they try to schedule it around local school districts' spring break. 

The "Buried Secrets" tours this time of the year have a special treat for guests - they're able to visit the prison's cemetery, which is never a part of normal tours, according to Bierle.

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One of the many stops on the tour is death row, where one of the prisoners, Raymond Snowden, brutally murdered a woman named Cora Dean after they got into a fight.

"He ends up pushing her into a car," said Ignacio, one of the tour guides, recounted. "She gets hurt, she gets upset and ends up kicking him between the legs, which upsets him. But she didn’t know he had anger issues."

"He ended up having a pocketknife in his pocket and he used that almost 2-inch blade to attack her. He ends up slicing her throat," she continued. "Eventually he went to court for it, stayed here for about five months, and two months later, he was sent to his execution through those doors to the gallows."

In the hospital wing of the prison, six men died from the Spanish flu epidemic during the 1910s.

According to the tour guide, one of those men, Frank Frisbee, is one of 55 confirmed prisoners buried on site of the Old Pen.

"He was an Irishman but because he got the Spanish flu, he had no family or friends and they ended up burying him in the cemetery because of that."

Bierle said they are constantly trying to update the number of deaths that happened at the prison. She said so far, they've confirmed 129 people died there during the 100 years it was open.

Bierle said she can't confirm if there is paranormal activity in the Old Idaho Pen, but the tour does stop at locations inside the prison that have a dark and long history and let people decide for themselves if there are supernatural forces inside the walls.

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Not all of the tales from prison are dark though, thanks to one feline inmate in particular.

"Behind the shirt factory is actually the burial of Dennis the Cat," Ignacio described. "Dennis was a kitten who was discovered by an inmate who was working in the chicken coop actually in this yard here. When they went through the gate, they checked his pockets but they didn't find the kitten so he was able to get the kitten back to his cell."

The tour guide said he was well-loved among all the inmates as well as the warden. Dennis even became a therapy cat for many of the prisoners.

After 16 years of serving time, Dennis passed away but did receive a proper burial on site.

People on the tour guide said they really enjoyed it and learned a lot of history they never knew before.

“I thought it was great," said Kristi Nuttall, one of the tour's members. "I never even knew there was one in all the years I’ve walked those foothills and come on field trips and all kinds of stuff - it was just really interesting."

One woman said she plans to come back and do more tours at the Old Pen.

“I’m a cat person so probably my favorite part was about the cats, the first one in particular about the one who’d been here 16 years, said Stacia Hanaway, who was also on the tour. "But outside of that, it’s really interesting that they don’t know who’s buried here – there are more unknowns than knowns.”

The "Buried Secrets" tours run through March 29. Tour times are daily and run each hour from 3 p.m. to 6 p.m.

Bierle said the first two tour times on Saturday sold out so it's best to buy tickets in advance, if possible.

Tickets for the tour can be purchased on the Old Pen's website.

Currently, the Old Idaho Penitentiary is teaming up with Boise State University students to find out exactly how many people were buried there.

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Historical experts and the students hope to unearth the prison's forgotten history and possibly find unknown graves that would add to the stories told in future tours.

Bierle said so far, the results show there are anomalies and a few soil disturbances between grave markers. The students will go back out and do more research to determine if those disturbances are additional burials.