One important aspect of Harry Grey's The Hoods, the inspiration for Leone's Once Upon a Time in America, is how fact and fiction merge within it. Given this, it was interesting to read a description of how two real-life gangsters, Lepke and Shapiro, met and elements of similarity with Noodles and Max in Leone's film; in Grey's book the two are already friends, whereas in Leone's film they are rivals when they first meet:
"Lepke took to stealing pushcarts, and one day, he tried to rob a pushcart that was already being robbed by another street tough named Jacob “Gurrah” Shapiro. The two became fast friends, and started a relationship that would last the rest of their natural lives.
Lepke and Shapiro teamed up, and became a menace to the downtown pushcart owners. They
tried to climb the ladder to bigger scores, but in 1918, Lepke was caught robbing a downtown loft, and as a result, he was sent to Sing Sing Prison for a five-year stretch.
Lepke's time in prison was the equivalent to a college education for criminals. When Lepke, at the age of 25, was released in 1923, he was now a hardened thug, with the knowledge to make it big in a life of crime. Lepke teamed up again with his old pal Shapiro, and they decided they could make a mint selling “protection,” to bakeries all throughout New York City." -- Joe Bruno Mobsters, Gangs and Other Creeps