In the 1850s, New York City was looking for a new hangman. The profession came with a real drawback in that when people knew his identity, they didn't want to be around him. So another hangman retired, and a young man who had worked at a slaughterhouse took the position. He worked for the city for decades, and became known as Monsieur de New York.
This guy took his work seriously. He designed a new gallows that killed quickly and thoroughly, and kept improving upon it. Although public hangings were no longer done, any execution inside the walls of the justice system were standing room only as the public clamored to get a restricted number of tickets. Monsieur de New York put on a show, dressed nattily for the occasion, and acted as a master of ceremonies. His reputation grew, although no one knew who he was. He preferred it that way. As the executioner's fame grew, he was enlisted to carry out federal executions, design gallows for other departments across the country, and even lent his name, or pseudonym, to U.S. Grant's presidential campaign.
Although several men claimed to be Monsieur de New York, and others were accused of that identity but denied it, we still don't know who was the celebrity executioner of New York. Read about Monsieur de New York's work and fame at Atlas Obscura.