Democrat Elizabeth Warren takes the stage after defeating incumbent GOP Sen. Scott Brown in the Massachusetts Senate race, during an election night rally at the Fairmont Copley Plaza hotel in Boston, Tuesday, Nov. 6, 2012. (Michael Dwyer/AP)

Elizabeth Warren’s race in Massachusetts may have been the most closely watched win by a female senator-elect from Tuesday night.

But her election points to another big win for women in the Senate. The returns so far show at least 20 women will be serving in the upper chamber come January, a historic high. All of the incumbents won their races, and the elections of Warren, Democrat Tammy Baldwin of Wisconsin, Republican Deb Fischer of Nebraska, Democrat Mazie Hirono of Hawaii and Democrat Heidi Heitkamp of North Dakota brought the count from 17 to 20. They made up for two women who are retiring (Olympia Snowe of Maine and Kay Bailey Hutchison of Texas) and added three additional women to the total.

Heitkamp’s win, called on Wednesday afternoon, means that women will now make up one-fifth of the Senate. That’s still a woefully small number of women leaders compared to the population they represent, but it’s impressive when compared with the past.

Twenty years ago, 1992 was dubbed the “Year of the Woman” when there were just seven women serving in the Senate. This election will put the percentage of women in the Senate even higher than that of the current House (16.8 percent), according to the Center for American Women and Politics at Rutgers University, and slightly less than the percentage of women holding gubernatorial slots (23.4 percent).

Tuesday’s results are good news for the simple fact that women are gaining, rather than losing, ground in such critical offices. Twenty percent is a new high that is significant. But to keep those numbers growing, even more needs to be done to fill the ranks of state offices with women who stand a chance at winning these top slots in the future.

While the numbers are being tallied from 2012 state races, it’s important to note that before Tuesday female representatives in state legislatures stood at 24 percent, just three percentage points higher than two decades ago, as Bloomberg BusinessWeek notes. So to get more women at the top, we have to keep filling the pipeline at the bottom with young women leaders as well.

Jena McGregor is a columnist for the Washington Post’s On Leadership section.

More from On Leadership:

A tale of two Obama victory speeches

What makes an excellent president

Like On Leadership? Follow us on Facebook and Twitter:

@post_lead | @jenamcgregor | @lily_cunningham