Hello. You did not inform the time period in which this increase in NOW membership occurred, which prevents me from telling you about a specific event. However, I will try to help you as best I can.
NOW refers to the National Organization for Women, which is an American institution that seeks to protect and strengthen the rights of women in the country. This institution had a large increase in membership in the 1960s because it was heavily influenced by civil rights movements. As civil rights was a very specific and recurrent subject at that time, many women, also socially devalued and prevented from having their rights, took advantage of this moment to claim their causes, which increased the number of adhesions and supporters to NOW.
