In 2012, around 53,950,000 people voted for a Democratic representative vs. 53,400,000 who voted for a Republican one. The Democrats won the House popular vote by over half a million votes. However, the Republicans won 54% of the seats and thus control the house (233 R vs. 201 D with 1 undecided at the time of writing).
President Obama won Pennsylvania by more than 5 points, but Democrats carried only 5 of the state’s 18 congressional seats.
Obama won Virginia, and Democrats took 3 of 11 House seats.
Obama won Ohio, but Democrats carried only 4 of 16 seats in Ohio’s House delegation.
While the above states were heavily gerrymandered by Republican controlled state legislatures, Democrats have similarly gerrymandered Illinois and Maryland.
* How Ridiculous Gerrymanders Saved the House Republican Majority.
* California Secretary of State redistricting page.
* State of California Citizens Redistricting Commission.
* State of California Citizens Redistricting Commission [PDF] Final report on 2011 redistricting, August 15th, 2011.
* The Public Mapping Project is developing District Builder, an open source software redistricting application designed to give the public transparent, accessible, and easy-to-use on-line mapping tools..
* DistrictBuilder is web-based, open source software for collaborative redistricting..
Some of the most gerrymandered districts in 2006: