The National Mall is an open-area national park in downtown Washington, D.C., the capital of the United States. Officially termed by the National Park Service the National Mall & Memorial Parks, the term commonly includes the areas that are officially part of West Potomac Park and Constitution Gardens to the west, and often is taken to refer to the entire area between the Lincoln Memorial and the Capitol, with the Washington Monument providing a division slightly west of the center.
The National Mall was where Deathstroke gunned down an assassin who had been impersonating a politician known as Senator Williams. The Williams doppelganger was going for a morning jog with then-President Bill Clinton with the intent of assassinating him. 
In 1997, a group of White Martians posing as a galactic super-hero team known as the Hyperclan landed in Washington, D.C. The team's leader, Protex addressed the entire world from the National Mall, indicating that they have come to heal the Earth from the dangers of ecological instability. In truth however, this was just part of a plot to turn public opinion against Earth's super-hero community, specifically, the JLA. 
The National Mall was also the site of the "Justice for All" rally where the young super-hero team Young Justice invited all active super-heroes in the country to join them in an assembly aimed at strengthening communications between the older and younger generations of heroes. The demonstration was interrupted when Klarion "Bum, Bum, BUM" the Witch Boy cast a spell that turned members of the JLA, JSA and the Marvel Family into teenagers. 
The National Mall was also one of the first targets of Circe's Amazon force during the Amazonian war against the United States. The Mall was overrun with bloodthirsty Amazon warriors who indiscriminately slaughtered everyone in their path.