From the Center for American Women and Politics: In 2020, women hold 127, or 23.7%, of the 535 seats in the 116th U.S. Congress, 26 of the 100 seats in the Senate, and 101 of the 435 seats in the House of Representatives.
For more interesting political statistics, the Center for American Women and Politics published the report, "Women in Elective Office, 2020", which shows clearly the slow, but seemingly steady ascent of the respresentation of women.
Condoleeza Rice was the first African-American Secretary of State, serving from 2005-2009. The first female Secretary of State was Madeline Albright (1997-2001), whose father, Josef Korbel, served as a mentor to Rice.
Janet Reno was the first woman US Attorney General. While her time in office was fraught with controversial issues, such as Waco siege, the Elian Gonzalez affair, and an information leak on the Centennial Olympic Park Bombing, which implicated a first responder, she still holds the title of longest serving Attorney General in the United States.
For the scope of this timeline, we will focus on formal political appointments, beginning in the 1910s.
Brochures from the National Women's Political Caucus of Santa Clara County Records, SJSU Special Collections & Archives.
Suffrage flyer from the International Museum of Women Records, SJSU Special Collections & Archives.
This photo is of Vera Daerr Buchanan, the first woman member to die in office. See more photos and facts at the United States House of Representatives: History, Art & Archives page, Women in Congress.