Opening the Door on New York's Private Clubs. A Continuous Lean. Dining at The Brook. The Brook was founded in 1903 by a group of prominent men who belonged to other New York City private clubs, such as the Knickerbocker Club and the 15 Oldest Private Clubs in NYC Untapped New York Members Only Mania: Why Are More Private Clubs Popping Up in New York? The New York Times Inside The Brook: The most private social club in NYC. When it comes to members only establishments, few are as exclusive (and understated) as The Brook, established in 1903 and defined by personalized *