Although hot dogs are a relatively recent invention, their precursor the sausage has been around for millenia. Historians have found references to sausages as old as 850 B.C. in Homer's Odyssey.
Regardless, the most oft credited inventor of the sausage is Gaius, the cook for Emperor Nero Claudius Caesar, in the year 64. Supposedly, Gaius noticed a pig roasting for the emperor's dinner had not been cleaned, and he rushed to gut the animal, whereupon he discovered the intestines were puffed up and hollow. He filled these with a mixture of ground meat and other ingredients to produce sausages.
19th and 20th Century
The early history of the modern hot dog is also in dispute. Most agree that the definition of the earliest "hot dog" is a sausage in a bun, rather than any particular combination of sausage ingredients. One name, however, rises above the others in hot dog history: Charles Feltman. The first Coney Island hot dog vendor, Feltman began in 1867 selling pies to Coney Island taverns out of an old cart. His customers began requesting sandwiches as well but Feltman, limited by the available space in the cart, knew he would be unable to hold a large volume or variety of sandwiches. His solution was to have a small charcoal stove and a tin box built into his cart to boil sausages and store rolls. Thus, the hot dog was born!
Feltman went on to build many businesses in Coney Island, including a hotel, many kinds of rides and various food stands. At his death in 1910, Feltman's business--which began with a modest pie cart--was valued at over a million dollars, or $21,645,764 in modern money!