How Come There are 2 Airports in NYC?

Most major cities have more than one airport. Chicago has O'Hare and Midway, but there are something like 10 airports within the city limits. DC has Reagan, Dulles and BWI. LA actually has 5 airports. When I was there last month, I flew into John Wayne International to avoid the chaos of LAX. I was in and out of the airport in no time. NYC actually has 6 airports that deal with commercial travel: JFK, LaGuardia and Newark are major hubs, but commerical traffic also flies into MacArthur, Stewart and Westchester.