Reconstruction:
The period (1865-1877) during which the states that had seceded to the Confederacy were controlled by the federal government before being readmitted to the Union.

Source: reconstruction. Dictionary.com. The American Heritage® Dictionary of the English Language, Fourth Edition. Houghton Mifflin Company, 2004. http://dictionary.reference.com/browse/reconstruction (accessed: March 29, 2009).