The house at 1651 Pennsylvania Avenue has been a neighbor of the White House since 1824 -- and at the center of Washington's political life for just as long.
Francis Preston Blair, a member of President Andrew Jackson's "Kitchen Cabinet," moved in during Jackson's second term. Blair continued to be an insider in the administrations of Martin van Buren and Abraham Lincoln.
The house stayed in the Blair family until 1942 when wartime demands upon the White House led President Franklin D. Roosevelt to seek housing for visiting foreign dignitaries. The State Department subsequently purchased Blair House.
But this role was interrupted from 1948 to 1952 when President Harry Truman moved in along with his family while the White House was being renovated.
Today, Blair House is the president's official guest house, hosting world leaders meeting with the occupant of 1600 Pennsylvania Avenue.
It also serves as a home for presidents-elect in the days before the inauguration as well as a respite for former first families during state funerals.