Illinois's new Legislative, Congressional and County Board Districts will go into effect in January 2013 when the winners of the November 2012 election are sworn into office.  The candidates for office in the March 20, 2012 Primary Election and November 6, 2012 General Election will be running in the new Districts which were drawn in 2011 following the 2010 US census. Due to a decline in the state's population from 2000 to 2010, Illinois's Congressional Districts were reduced from 19 to 18.

The following link will take you to the Illinois State Board of Elections Interactive GIS Map depicting district boundaries.  www.elections.il.gov/gis.aspx.

You will be able to enter an address and see the applicable new Congressional and Legislative districts for that address.