Maryland adopted new Congressional districts on October 20. 2011 (per U.S. Constitution Article I, Section 2) and new State Legislative districts on February 24, 2012 (per Maryland Constitution Article III, Section 5) based on the changes in population reported in the 2010 U.S. Census and in accordance with Maryland’s “No Representation Without Population Act” of 2010.
The Maryland Department of Planning (MDP) is the repository of the 2011 Congressional and 2012 Legislative districts as well as historical reapportionment and redistricting maps and data. MDP is Maryland's designated State Agency coordinator for the Census Redistricting Data Program with the U.S. Bureau of the Census.