It's a matter of some dispute, but Charles Feltman is often credited with inventing the hot dog. Whether or not the German immigrant was the first person to put a sausage in a bun, he began selling the creations to Coney Island beachgoers sometime around 1870. Finding success as a wiener slinger, he expanded his operations into what eventually became a massive 8,000-seat restaurant complex that was known for its seafood but, of course, still served plenty of hot dogs as well. (The last remaining building from the complex, a kitchen, was torn down a few years ago. Officials from the Coney Island History Project staged a hoax, reported as fact by CNN, in which they "found" a 140-year-old frankfurter preserved in ice beneath the leveled building. They had actually prepared the ice-encased dog elsewhere and snuck it into the demolition site.)
Feltman died in 1910, but his restaurant stayed in business, and it was a few years later that a young Polish immigrant named Nathan Handwerker found work there slicing rolls. Supposedly with some encouragement and borrowed money from his then-unknown co-workers Eddie Cantor and Jimmy Durante, Nathan opened his own hot dog joint in 1916 at the corner of Surf and Stillwell Avenues, where he and his wife served up frankfurters for just a nickel apiece, half the price his former employer charged.
According to legend (and Nathan's grandson), with some variations from one telling to another, people were initially skeptical about the quality and contents of a wiener that could be sold for a mere five cents. To alleviate these concerns, Nathan hired people to dress as doctors and eat hot dogs in front of his stand, giving the impression that medical professionals considered his food perfectly healthy. Before long, with the arrival of the subway in Coney Island (and with the terminal station located right across the street), the dogs started selling like crazy, and now, almost a century later, Nathan's Famous remains a household name.