Extract the answer to the question from the following context. Question: Which century preceded the 21st century? Context: 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.
The answer to this question is:
20th century