This is from the Aaron Siskind Foundation website:

Photographer and educator Aaron Siskind (1903-1991) holds a preeminent place in the history of American photography.

Beginning his photographic career in the 1930’s as a social documentarian with the New York Photo League, he ultimately radicalized the medium by emphasizing the photograph as an abstract form of expression and an aesthetic end in itself.

Siskind taught in New York City’s public schools for 25 years before becoming recognized as a photographer and then a gifted pioneer of photographic education.

His vision and methods have and will continue to inspire and instruct future generations of artists and teachers.