National Mall
Pierre L'Enfant, the man who planned Washington D.C., wanted to have a park in the middle of the city.  However, the National Mall was not always a park.  In the 19th century, there was a railroad that ran through the Mall.  Cows also grazed (ate grass) on the Mall.  There was a large market on one side of the Mall.  During the American Civil War, there were many buildings on the Mall.  There were even slaughterhouses on the Mall - places where animals are killed and turned into meat.  In 1901, the Senate passed the McMillan Plan.  This cleaned up the National Mall and moved the railroad to Union Station.