The motorcade left Love Field shortly after 11:50 a.m., and proceeded through residential neighborhoods, stopping twice at the President’s request to greet well-wishers among the friendly crowds. Each time the President’s car halted, Secret Service agents from the “followup” car moved forward to assume a protective stance near the President and Mrs. Kennedy. As the motorcade reached Main Street, a principal east-west artery in downtown Dallas, the welcome became tumultuous. At the extreme west end of Main Street the motorcade turned right on Houston Street and proceeded north for one block in order to make a left turn on Elm Street, the most direct and convenient approach to the Stemmons Freeway and the Trade Mart. As the President’s car approached the intersection of Houston and Elm Streets, there loomed directly ahead on the intersection’s northwest corner a seven-story, orange brick warehouse and office building, the Texas School Book Depository. Riding in the Vice President’s car, Agent Rufus W. Youngblood of the Secret Service noticed that the clock atop the building indicated 12:30 p.m., the scheduled arrival time at the Trade Mart. The President’s car which had been going north made a sharp turn toward the southwest onto Elm Street. At a speed of about 11 miles per hour, it started down the gradual descent toward a railroad overpass under which the motorcade would proceed before reaching the Stemmons Freeway. The front of the Texas School Book Depository was now on the President’s right, and he waved to the crowd assembled there as he passed the building. Dealey Plaza--an open, landscaped area marking the western end of downtown Dallas--stretched out to the President’s left. A Secret Service agent riding in the motorcade radioed the Trade Mart that the President would arrive in 5 minutes.