Was slot controlled up until 1970, then relaxed. Slots were re-introduced in 2008 after the two NJ
Senators asked the FAA to do it as they were concerned that whatever traffic JFK
lost from new slots would be shifted over to EWR
and make delays even worse than they already were. Weird thing is that EWR
always had the worst delays in the nation for so many years, but the FAA did nothing and probably wouldn't have done anything about it until those Senators got involved.
I believe HPN
also has some sort of slot controls, but mostly because of NIMYs.