This is the Dallas County Administration Building formerly known as The Texas School Book Depository. This building is one of the most heavily visited and most photographed landmarks in Dallas.
According to wikipedia, In 1963 the building was in use as a multi-floor warehouse for the storage of school textbooks and related materials and an order-fulfillment center by the Texas School Book Depository Company. Some time after the company moved in, it was found that the upper floors had sustained oil damage from items stored there by the previous tenant, a wholesaler grocer. To protect the company’s books (stored in cardboard boxes) from oil seeping up from the floor, a process was begun to cover the floors with plywood. Immediately prior to the Presidential visit, work had begun on the west side of the sixth floor, “leaving the whole scene in disarray, with stock shifted as far as the east wall, and stacks in between piled unusually high.
On November 22, 1963, Lee Harvey Oswald, a 24-year-old former U.S. Marine who was working as a temporary employee at the building, fired the shots from the sixth floor that killed the 35th President of the United States, John F. Kennedy.