Nowhere has the red/blue divide between the states been more apparent than on contentious social issues such as gun control, abortion, gay marriage, and immigration.
With 37 states under one-party control, lawmakers responded aggressively to national events and political developments in Washington.
After the school shooting in Newtown, Conn., Democratic states such as New York, Connecticut and Maryland passed sweeping new gun laws. "Nothing focuses your attention like 20 babies being killed," said Connecticut Gov. Dannel Malloy, after the mass shooting at Sandy Hook Elementary School in his state.
Republican-dominated states, meanwhile, looked to block federal laws and loosened numerous restrictions on guns and ammunition.
Arkansas and North Dakota enacted the strictest limits on abortion (at 12 weeks and six weeks from conception, respectively), in laws that may test Roe v. Wade. In 2014, North Dakota voters will consider a measure that would enshrine in state law the idea that life begins at conception, effectively outlawing abortion. But New York, Washington and California looked to expand abortion access, particularly in the new health insurance exchanges that will launch in October as part of the Affordable Care Act.