The House swore in the second-ever Muslim to its ranks, Rep. Andre Carson, D-Ind.
Carson was elected Tuesday in a special election to succeed his grandmother, Rep. Julia Carson, who died last year after serving more than 11 years in the House.
Rep. Keith Ellison, D-Minn., became the first Muslim elected to Congress when he was elected in 2006.
Carson is 33 and was an Indianapolis city councilman.
He is expected to face a strong challenge in the general election this fall.
The swearing-in of Carson brings the current membership of the House to 431 members, including 233 Democrats and 198 Republicans. There are four vacancies.
Two of the vacancies are in Louisiana: Bobby Jindal, who became governor, and Richard Baker who resigned last month. An open seat remains in Mississippi after Roger Wicker was appointed to the Senate to succeed Trent Lott. The remaining open seat is in California: Democrat Tom Lantos died last month.