H.H. Holmes is often called America's first serial killer, and his "Murder Castle" built for the 1893 Chicago World's Fair is the stuff of legend. But how much of the story is true? Holmes, born Herman Mudgett, was a charming con artist who built a three-story building with shops, apartments, and a supposed hotel [citation:3][citation:15]. Sensationalist newspapers claimed it had trapdoors, gas chambers, and soundproof rooms—perfect for killing tourists [citation:2][citation:8]. In reality, the building was unremarkable, and Holmes likely killed around nine people he already knew, not 200 strangers, mostly for financial gain [citation:7][citation:15]. But the legend of the Murder Castle remains a terrifying chapter in true crime history.