Fannie Mae made its much-anticipated site selection for relocating its national headquarters in Washington, DC. The mortgage GSE announced it has selected Carr Properties’ proposal for the redevelopment of The Washington Post’s current headquarters at 1150 15th St. NW. Carr plans to demolish the existing buildings on the prominent corner site to make way for the residential mortgage creditor’s new 700,000-square-foot headquarters, a move that will…