Senator Barbara Mikulski, Maryland Democrat, to Retire

Senator Barbara A. Mikulski, the animated and occasionally irascible Democrat from Maryland who rose from being a community organizer to become the longest-serving woman in Congress, announced on Monday that she would retire when her term ends in 2017.

The surprising decision came just a few months after Republicans gained control of the Senate, reducing Ms. Mikulski from chairwoman to of the powerful Appropriations Committee, where she had been the first woman to lead the panel, to ranking member.

Ms. Mikulski, 78, announced her decision to not seek a sixth term on Monday mornin