One of the most common arguments waged by feminist groups about the continuing need for women’s right is a lack of representation in many typically male-dominated industries. Much of this glass-ceiling breaking is in the corporate world, but women still remain underrepresented in the body meant to give an equal voice to all: Congress.

That’s not to say there hasn’t been a hasty and significant increase in the number of women in Congress over the last few decades. While female leaders in the Senate and House of Representatives emerged very early in American history, they held less than 10 percent of total seats in both legislative bodies well into the 90s, according to data compiled Pew Research Center.

Huge strides — including an enormous 18 seat gain in the House of Representatives in “Year of the Women” 1992 — have more than doubled those numbers. Today, women make up almost exactly 20 percent of the total number of Congressional representatives. Furthermore, they wield more influence with these positions than ever before: Nancy Pelosi became the first female Speaker of the House in 2007.

The high penetration of women in congress is even more impressive considering that before, female representatives often inherited their seat. Pew notes that less than 50 years ago, it was still quite common for a wife or daughter to take the seat out of tradition when their Congressman spouse or father passed away.

“Well into the 1970s, one of the most common ways for a woman to enter Congress was by succeeding her late husband or father, either by election or appointment. Of the 90 women who served in the House between 1916 and 1980, 31 were initially elected to their husband’s seat after he died; three were chosen to replace their husbands on the ballot when they died before Election Day; and one (Winnifred Mason Huck of Illinois) was elected in 1922 to fill the last four months of her late father’s term. (Another early congresswoman, Katherine Gudger Langley of Kentucky, won her husband’s seat in 1926 after he resigned following his conviction for violating Prohibition laws.)”

That’s not say that the women in Congress who didn’t get there by election didn’t mean business. Margaret Chase Smith of Maine and Lindy Boggs of Louisiana were both re-elected several times after taking over their husband’s slots, reported Pew.

Splits on party lines have swapped significantly over the years. Republican women made up the majority of female-held seats until the Great Depression, and the number of conservative and liberal women stayed relatively even until the current boom of women in Congress — Democrats account for 69 percent and 67 percent of the women elected to the House and Senate since 1990, respectively.

[Images via Flickr, Pew Research Center, and Love4Utah]