Dr Henry Howard Holmes was an American serial killer of the 19th century, that’s the 1800s for people that get confused by these things. Actually, his name was Herman Webster Mudgett, but like all good serial killers he needed an alias (actually he changed it to avoid prior scandals). He is most famous for creating the “Murder Hotel”. For the 1983 world fair in Chicago, he built a hotel where his victims would come and find themselves trapped for him to kill! He purchased a two-story building, added a third floor, and kept firing the architects and hiring new ones so that no one would know the true design of the hotel. He was crazy, not stupid.
He’s known as America’s first serial killer, admitting 28 murders, though it’s believed he was responsible for many more.
Some rooms were sealed shut and were used as gas asphyxiation chambers, others were lined with iron plates and had blow torches built into the walls to burn his victims. The rooms had alarms to alert him if anyone tried to escape. The basement had a surgical table spattered with blood, jars of poison, boxes of bones, he even had his own crematorium, vats of acid and lime pits that could dissolve bodies. Chutes from the rooms led to the basement for efficient disposal.
Edit: A reader has raised that there is also speculation that HH Holmes may also be Jack the Ripper. There are similarities between the two in the manner of their murders, and the timeline does not cause any issues to this theory. As with all Jack the Ripper theories though, there is no concrete evidence of his identity so it is up to you to believe if you want to. Thanks to Kris Wright for contacting me about this.