Gramercy Park is one of only two private parks in NYC (the other being Sunnyside Gardens in Queens). There are 383 keys to the Park, which are solely reserved for those who live along the border of the Park and pay an annual fee. Commerical photography is prohibited, so the public never had a peek beyond the gates. That is until 2014, when, using a borrowed key and a smartphone, computer programmer Shawn Christopher posted a panaromic video online. Mr. Christopher thus trumped Robert DeNiro and Woody Allen who had been denied permission to film in the Park.
Gramercy Park occupies 2 acres between 20th and 21st, from Gramercy Park West to Gramercy Park East. The area was a swamp until Samuel B. Ruggles, a developer and advocate of open space, bought the space in 1831 and spent $180,000 in landscaping to build a park that would accommodate the northward growth of Manhattan. He then deeded the land to the owners of the 66 parcels of land surrounding the Park. Development of those lots began in the 1840s, and in 1844 the gates of the Park were first locked.
An interesting tidbit: in the center of the Park is a statue of Edwin Booth, older brother of John Wilkes Booth. The elder Booth was a popular Shakespearean actor and founded the Players Club on Gramercy Park South. The Players Club presented the statue of Booth as Hamlet to the Park in 1918.