The present East Wing was added to the White House in 1942 in part to balance the enlarged West Wing and in part to cover the construction of an underground air-raid bunker now known as the Presidential Emergency Operations Center.
Among its uses, the East Wing has sometimes housed the offices and staff of the first lady and provides a covered entrance to the White House that allows guests to easily flow through the mansion for large social events.
President Jefferson added colonnaded terraces to the east and west sides of the White House, but no actual wings.