Sources: Democratic Sen. Barbara Mikulski, longest serving woman in Congress, to retire

March 2, 2015       BREAKING NEWS Sources: Democratic Sen. Barbara Mikulski, longest serving woman in Congress, to retire This is a developing story and we expect to have more information soon. Go toNBCNews.com for further developments.     Keep Reading             For Breaking News, the moment it happens, follow @NBCNEWS Follow @NBCNEWS     More Top Stories     Dramatic Video Shows Fatal Police Shooting on Skid Row > More Winter Storms on the Way for Large Swaths of U.S. > Growing Billionaires List Welcomes MJ to Its Ranks > Watch Amazing Moment Skydiver Is Saved Midair > Monday's Top 6 News Stories >