Maryland, like all states, must draw new Congressional districts (U.S. Constitution Article I, Section 2) and State Legislative districts (Maryland Constitution Article III, Section 5) based on the principal of one-person one-vote following the decennial Census of the United States.

The Maryland Department of Planning (MDP) is the repository of Reapportionment and Redistricting maps and data products. MDP is Maryland's designated State Agency coordinator for the Census Redistricting Data Program with the U.S. Bureau of the Census.

The redistricting process began with the Census count in spring of 2010 and then the delivery of the population data in May 2011. After holding public hearings, receiving 3rd party plans and a review and analysis of proposed plans, the Governor’s Redistricting Advisory Committee delivered proposed Congressional and Legislative plans to Governor Martin O’Malley. The Governor then submitted his plans to the Maryland General Assembly as bills for passage into law . The new districts were adopted by the General Assembly and Governor O’Malley in time for the Congressional primary of 2012 and the State Legislative Election of 2014.

• Overview of the 2010 Census Redistricting Data Program - U.S. Bureau of the Census
• Timeline

Congressional Redistricting Plan Archives

• Governor's Statement (October 15, 2011)
• House Bill 1 (2011 special session)
  An emergency house bill concerning Congressional Districting Plan
• Senate Bill 1 (2011 special session)
  An emergency senate bill concerning Congressional Districting Plan
• Report of Maryland Precinct Population Data
• Download the Governor's Statewide Congressional map
• The Governor's Redistricting Advisory Committee (GRAC) recommended Congressional redistricting plan (October 4, 2011)
• Comparison of Congressional District plans by Governor O'Malley and the Governor's Redistricting Advisory Committee (October 15, 2011)