“A very important part of American history happened here in Chicago in 1886 on May 4. I think it’s also important for people to understand that event is why we have Labor Day, and I think probably 99.9 percent of the people, if you ask them, ‘What is the origin of Labor Day?,' they wouldn’t know,” Wolter, a forensic geologist, told the Tribune while he filmed here in March. “But after this episode they are going to know, and they’re going to know a lot more about what happened here and hopefully they’re going to find out who threw that bomb.”