First Wave- 1800's-1920's. The passage of the 19th Ammendment is commonly seen as the culminating event of this phase.
Second Wave- 1950's-1980's.This is often seen as the high point of the Women's Movement in the US. The failure of the Equal Rights Ammendment's passage is seen as the endpoint of this period.
Third Wave- 1990's-present. Often seen as a more theoretically-driven phase, sometimes incorrectly referred to as post-feminism.