Plimpton was born in New York City on March 18, 1927, and spent his childhood there, attending St. Bernard's School and growing up in an apartment duplex on Manhattan's Upper East Side located at 1165 Fifth Avenue.
Plimpton lahir di New York City pada 18 Maret 1927, dan menjalani masa kecilnya di sana, masuk St. Bernard's School dan dibesarkan di sebuah apartemen di 1165 Fifth Avenue, Upper East Side, Manhattan.