What event sparked the Gay Liberation movement?

The stock answer is police harassment at the Stonewall Bar on Christopher Street in New York's Greenwich Village in June 1969. There were, however, lesser none events that occurred before then. The first group of gays to protest for rights in public were known as the Mattachine Society. They dressed in business attire and picketed against employment discrimination, particular with regard to civil servants as early as the 1950s.