Al Capone redifined what it meant to be a gangster. During the second half of the 1800's, gangs were run mainly by leaders of a city's immigrant populations. Every immigrant group had a gang in one or more cities. The gang did normal gang stuff -- charge protection money, run brothels -- but they were often supported by the community because the gangs had influence with political figures. Politicians figured things like prostituion would go on anyway, and if it was to happen they would rather it happen in the Italian/Chinese/Jewish/any immigrant part of town than the "good" neighborhoods. So the gangs had a mutual understanding with the politicians, and the members of the community had an understanding with the gangs. Everyone helped everyone. Gangs were not nationally networked or anything like that until prohibition.
When prohibition came around, there was a real chance to make money in illegal activities. Gang leaders were already the wealthiest in their community, but they weren't making nearly as much money as bootlegging potentially could. This is where Al Capone comes in. Everyone was running around trying to make money off illegal alcohol, but Capone was simply the best. He used completely brutal tactics to eliminate his enemies, and his gang existed for the sole purpose of running an illegal business. He had no unspoken deals with politicians or members of the community, except for the ones he made through bribes. Capone was so successful in running his empire that by the middle of prohibition, he was one of the richest men in the country and practically owned Chicago. He singlehandedly created organized crime as we know it in this country. He was also known as Scarface (though he hated the name, and no one said it to his face), and Tony Montana was modeled after him.
Al Capone is the true Original Gangsta.