@DrDan Thank you so much! Great info. When my family moved to the neighborhood, it was at 50 Van Cortlandt Park Ave West and felt like a regular supermarket (like a C Town–which it later became). I was too young to remember if that iteration was operated like a coop. Just a very interesting slice of old NYC life.
Thank you all so much! This is great. I absolutely will get in touch the librarian at the Leonard Lief Library. Thanks so much for that resource (and yes, I am interested in the grocery store that was connected to the Amalgamated Co-ops).