Seniority in both houses of the United States Congress is valuable as it confers a number of benefits and is based on length of continuous service, with ties broken by a series of factors.
In the House, Edith Nourse Rogers, who served 35 years from 1925 to 1960 as one of the first women elected to Congress (and the first woman elected from Massachusetts), was the longest-serving female Representative upon her death in office in 1960.
Her record was surpassed in 2018 by Marcy Kaptur of Ohio, who has served in the House since 1983.
Her record was surpassed in 2011 by Barbara Mikulski of Maryland, who served for 30 years from 1987 to 2017.
Across both houses of Congress, Rogers' 35 years of service from 1925 to 1960 was the longest for a female member when she died in office in 1960.