The same person oversaw both the Manhattan Project and the Pentagon’s construction

 The Pentagon was built on land occupied by the descendants of former slaves.
During the Civil War, a settlement known as Freedman’s Village sprung up on Robert E. Lee’s former estate, as escaped slaves made their way to the non-Union held territory. Twenty yeas after the war, these settlements were uprooted, and several predominately black neighborhoods, including Queen City and the seedier, red-light district of Hell’s Bottom, formed nearby in what became known as East Arlington. When the Pentagon’s planners realized that the original site selected for the massive complex was not large enough, the government agreed to evict more than 150 families from East Arlington and appropriate their land.

5. The same person oversaw both the Manhattan Project and the Pentagon’s construction.
While Somervell was officially in charge of the Pentagon project, it fell to one of his subordinates, the then Major Leslie Groves, to make it a reality. Groves oversaw the day-to-day construction of the site, successfully dealing with a series of strikes and managing the many strong-willed military figures exerting pressure on him to complete the project ahead of time. While still working on the Pentagon, Groves was also put in charge of the Manhattan Project, America’s successful effort to develop the world’s first atomic bomb. Groves was involved in nearly every aspect of the top-secret project, selecting and constructing clandestine sites for the research facilities and its workers across the country.

The 9/11 attacks occurred on the 60th anniversary of the groundbreaking.
On September 11, 2001, the Pentagon was nearing the end of its first full-scale renovations when American Airlines Flight 77 smashed into the building’s east side, which was unoccupied due to the construction. Nearly 200 people lost their lives in the attack, though the recently installed security improvements that were part of the renovation project, including reinforcing the building’s concrete and installing blast-proof windows and walls, undoubtedly saved hundred of lives. Plans were soon underway for an extensive reconstruction program, dubbed the Phoenix Project, which was completed in February 2003 at a cost of $5 billion—five times the cost of the original building.