With today's skyrocketing rents and ever-changing bar scene, it's hard to latch onto anything with consistency in this city, especially where latching = drinking.
But website I Quant NY solved that and used New York State's open data website to find out the start dates of all of NYC's liquor licenses to determine which spots in each 'hood (defined by a Pediacities dataset) have the longest-standing liquor licenses, which basically means the most staying power under the current owner. The catch is this doesn't necessarily mean the absolute oldest bars or restos, but those that have had the longest continuous liquor licenses and a specific start date on record.
The oldest overall license in the city belongs to the Harmonie Club (dating back to 1933!) in the UES, while the oldest beer license is represented by Nathan’s Famous in Coney Island, which dates back to 1934. There were also a few obvious, classic spots like Blarney Stone in the Financial District (1969) and The Palm in Midtown (1934), as well as some really odd discoveries like an Applebee's in Rego Park (2003).