The name "Mattachine" came from a group of medieval men who held dances and rituals and would wear masks.
Early Mattachine meetings were simply discussion groups, but later the organization moved into activism. Branches of the organization formed all over the US in places like New York, San Francisco, Philadelphia, Washington, DC and Chicago. They fought police harassment, employment discrimination, the classification of homosexuality as a disorder by psychiatrists and government policies against hiring gays.
Although a few women were involved in the Mattachine Society, it was a group primarily of men. As the gay rights movement picked up motion after Stonewall, Mattachine was seen as conservative by many. By the 1980s, most branches had dissolved.
Source: Gay America by Linas Alsenas