Like Black History Month in February, March is designated Women’s History Month by presidential proclamation and given a theme.  This year’s theme is Valiant Women of the Vote: Refusing to be Silenced. And, like Black History Month, Women’s History Month is designated as a time to honor the contributions women have made in American history.

In 1978, the Education Task Force of the Sonoma County (California) Commission on the Status of Women (whew! Try saying that five times fast!) organized a Women’s History Week celebration. The week of March 8 was selected to correspond with International Women’s Day. The movement spread and, by the next year, other cities started their own Women’s History Week.

In 1980, women’s groups and historian led by the National Women’s History Project (now known as the National Women's History Alliance) secured national recognition, and in February that year, President Jimmy Carter issued the first Presidential Proclamation declaring the Week of March 8, 1980 as National Women’s History Week.

Subsequent presidents proclaimed a National Women’s History Week every March until 1987, when Congress passed Public Law 100-9, designating March as Women’s History Month. Between 1988 and 1994, additional resolutions were passed by Congress authorizing the sitting president to proclaim each March Women’s History Month. Since 1995, each president has issued an annual proclamation.

Source: womenshistory.org