Please answer the following question: I know that the answer to the question "In which century did organized crime not fall in New York?" is in "Organized crime has long been associated with New York City, beginning with the Forty Thieves and the Roach Guards in the Five Points in the 1820s. The 20th century saw a rise in the Mafia, dominated by the Five Families, as well as in gangs, including the Black Spades. The Mafia presence has declined in the city in the 21st century.". Can you tell me what it is?
A:
20th century