The New York Education Association/New York (NYEA, later NEA/NY) was the product of the tensions between the National Education Association (NEA) and the American Federation of Teachers (AFT). Those tension at the national level were, in turn, a result of the merger of the NEA's New York State Teachers Association (NTSTA) and the AFT's United Teachers of New York (UTNY) to form the New York State United Teachers (NYSUT) in 1972. Eventually, in 1976, NYUST disaffiliated from NEA, keeping only its AFT affiliation.
In response to the disaffiliation NEA set up a rival union in New York, NEA/NY, and got some locals to leave NYSUT for the new union. This did not work as well as the NEA leadership had hoped and membership in the new union was stagnant while NYSUT grew. Finally, in 2006, a new merger brought the 35,000 NEA/NY members back into NYSUT.
From the guide to the NEA/NY Audio-Visual Materials, 1989-1995, (Kheel Center for Labor-Management Documentation and Archives, Cornell University Library)