Republican Martha McSally speaks to the media after a debate in October with Democratic incumbent Ron Barber on the University of Arizona campus in Tucson. (Mike Christy/Arizona Daily Star via Associated Press)

Republicans clinched their 247th U.S. House seat on Wednesday when GOP challenger Martha McSally officially unseated Rep. Ron Barber (D-Ariz.), bringing to an end the final unresolved congressional election of the midterms and handing the GOP its largest majority in the chamber since the Great Depression.

McSally's narrow win, which came after a recount, means that House Republicans will begin the 114th Congress with a 247-188 advantage over Democrats. It is the largest GOP majority since Republicans claimed 270 seats in the 1928 election.

“We’re grateful to everyone who devoted their time and resources, especially during the extended vote and recount processes, to get us over the finish line,” McSally, a retired Air Force colonel who lost a close race to Barber in 2012, said in a statement.

In his own statement, Barber congratulated McSally.

"This result is not the one we hoped for, but we take solace in having spoken out loud and clear for the principle that every legal vote should be counted," he said.

McSally led Barber by fewer than 200 votes after ballots were tallied, triggering the recount that confirmed her victory.