The 2000 presidential election was determined by the contested results of

The correct answer is Florida. 
During the election, there was a period of vote recounting in Florida that occurred during the weeks after Election Day.  The Florida vote was ultimately settled in Bush's favor by a margin of 537 votes when the U.S. Supreme Court, in Bush v. Gore, put to a halt a recount that had been initiated upon a ruling by the Florida Supreme Court.