Kathy Santini-Richardson knows where to find ghosts in Chicago.

She’s a ghost hunter, and one of her favorite spots is the alley behind the Oriental Theatre.

In 1903, the Iroquois Theatre opened on that site. That same year, a fire in the theater killed more than 600 people.

When her firm, Confidential Paranormal Investigators, checked out that location, she said the team experienced “shadow people” and unexplained lights and sounds throughout the night.

“You don’t even have to go in the theater to feel the activity,” said Santini-Richardson. “Just going by it, and in the alley, you can feel the energy.”

She said she believes the tragedy has caused the restless spirits to remain. She said most of the activity during their investigation took place as she read the names of the victims out loud.

Like many ghost enthusiasts, Santini-Richardson was raised around the paranormal. She said her grandmother lived in a haunted house, and paranormal experiences became a part of everyday life. She attended a ghost-hunting class before founding Confidential Paranormal Investigators in 2006. They’ve investigated private locations as well as some of Chicago’s most notorious public haunts.

They’re not alone; Chicago is home to more than a dozen ghost-hunting teams.

“You don’t have to believe in ghosts,” said Ursula Bielski, founder of Chicago Hauntings bus tour company. “But you cannot deny that Chicago is haunted by all of the tragic events that happened in the past.”

Bielski has authored 10 books on Chicago’s ghost lore and cemetery history. She founded her tour company in 2003 by buying a school bus and painting it black. In it, she and her husband, David Cowan, drive ghost enthusiasts around to some of Chicago’s many tragic sites.

Some of those sites have been changed or been covered up with “something more positive,” Bielski said, “but that’s not enough for the dead.”

For instance, the Chicago River site where the excursion boat Eastland capsized in 1915, killing 844 people, is remembered with historical markers but also is part of a festive riverfront.

Bielski is astounded by how many of her tour guests have had personal paranormal experiences. She said she’s had some experiences herself; one came after showing a tour group around the garden area of Jane Addams’ Hull House, 800 S. Halsted St., when she brought home a hitchhiking ghost.

According to her, the garden near Hull House is thought to be a Native American burial ground where apparitions can be seen thanks to an “inter-dimensional doorway.” Bielske said mediums advise those who visit the garden to pray before entering.

One day, Bielske did not. She went to bed that night and awoke at 4 a.m. with a headless man standing on her chest.

Bielske said Hull House is still one of her favorite haunted locations in the Chicago area. Another is Bachelor’s Grove Cemetery in Midlothian.

Several ghost hunters also cited Bachelor’s Grove. Bielske said visitors often see phantom cars, mysterious lights or a woman in white.

Nicole Tito’s fascination with ghost stories also began at a young age, with her father showing her places like Bachelor’s Grove and Resurrection cemeteries. Today, she’s an electronic voice phenomenon specialist for the American Spectral Society.

“A lot of my family is buried at Resurrection Cemetery, so we would go there all the time as kids,” Tito said. “I really like the story of Resurrection Mary. She’s one of the most well-known Chicago ghosts.”

According to Tito, Resurrection Mary is a woman drivers sometimes encounter hitchhiking along Archer Avenue, going toward Resurrection Cemetery. The woman enters the car and exits once the driver has reached the front gates of the cemetery, 7201 Archer Ave.

One of Resurrection Mary’s supposed haunts, the Willowbrook Ballroom in Willow Springs, 8900 S. Archer Ave., was gutted by a fire on Friday.

The American Spectral Society has investigated several local businesses; one of Tito’s favorite recordings was made at a vacant building at 2600 S. Wentworth Ave.; it had been the site of Ethyl’s Party, a funeral-home-turned-bar once owned by her family.

On the recording, Tito said, a woman’s voice can be heard saying “hi” — but, Tito said, she was the only female investigator present. She didn’t even hear the voice at the time, only when playing back the recording.

The professional ghost hunters know that around Halloween, amateur ghost seekers will be out looking for paranormal experiences.

They should be careful, the pros advise. Don’t trespass, they say, and don’t go alone.

“People get lost following lights in the woods,” Bielske said. “It’s better to have someone with you.”