One of the most striking features of the new class is its litany of firsts.

Ilhan Omar of Minnesota and Rashida Tlaib of Michigan are the first Muslim-American women ever elected to Congress; Ms. Omar, a state legislator, will also become the first Somali-American in the House. Like her predecessor, Keith Ellison, she has said she would likely be sworn in using a Quran.

In the suburbs of Kansas City, Sharice Davids, an openly gay woman and member of the Ho-Chunk Nation, toppled a Republican incumbent, Representative Kevin Yoder, to become one of the first Native American women to serve in Congress. The other is Deb Haaland of New Mexico, who will replace Michelle Lujan Grisham, just elected governor.

“We have a record-breaking number of women of color going to Congress who will be sworn in in January,” Ms. Haaland said in an interview. “Considering the fact that Native women have never had a voice in Congress for 240 years, it’s significant that we have an opportunity to bring that voice to the table.”

Among those women of color is Ayanna Pressley, who in 2009 became the first black woman elected to the Boston City Council. Then she stunned the Massachusetts political establishment when she beat Representative Michael Capuano in a primary earlier this year. Known for her fiery speaking style, she is, like Ms. Ocasio-Cortez, a darling of the progressive left, and she said in an interview that she is eager to bring her voice — and her passion for issues like overhauling the criminal justice system — to a Capitol that is still an overwhelmingly white male world.

“Washington is only a microcosm of society at large, and navigating these waters and terrain is not completely alien to me,” she said. “The corridors of power and most decision-making tables are dominated by white men. That was true when I was elected to the Boston City Council, and they enthusiastically embraced my agenda.”

Though no one is keeping records, Antonio Delgado of New York, a former Rhodes Scholar and Harvard-educated lawyer, is almost certainly the first rapper ever elected to Congress. His rap career was brief, but it did provide fodder for attacks from Republicans.

There are at least four people who identify as lesbian, gay or bisexual in the new Democratic class; they include Angie Craig, a health care human resources official who ousted a Republican incumbent in the suburbs of St. Paul, Minn. She said she takes pride in being another first: the first lesbian mother in Congress. She and her wife have four sons.