<P> In 1909, President William H. Taft agreed to meet with Mexican President Porfirio Díaz in El Paso, Texas and Ciudad Juárez, Mexico, the first meeting between a U.S. and a Mexican president and also the first time an American president visited Mexico . But the historic summit resulted in serious assassination threats and other security concerns for the then small Secret Service, so the Texas Rangers, 4,000 U.S. and Mexican troops, BOI agents, U.S. marshals, and an additional 250 private security detail led by Frederick Russell Burnham, the celebrated scout, were all called in by Chief John Wilkie to provide added security . On October 16, the day of the summit, Burnham discovered a man holding a concealed palm pistol standing at the El Paso Chamber of Commerce building along the procession route . Burnham signaled a Texas Ranger, Private C.R. Moore, and the two men captured and disarmed the assassin within only a few feet of Díaz and Taft, preventing the shooting of both Presidents . </P> <P> In 1950, President Harry S. Truman was residing in Blair House while the White House, across the street, was undergoing renovations . On November 1, 1950, two Puerto Rican nationalists, Oscar Collazo and Griselio Torresola, approached Blair House with the intent to assassinate President Truman . Collazo and Torresola opened fire on Private Leslie Coffelt and other White House Police officers . Though mortally wounded by three shots from a 9 mm German Luger to his chest and abdomen, Private Coffelt returned fire, killing Torresola with a single shot to his head . As of 2017, Coffelt is the only member of the Secret Service killed while protecting a US president against an assassination attempt (Special Agent Tim McCarthy stepped in front of President Ronald Reagan during the assassination attempt of March 30, 1981, and took a bullet to the abdomen but made a full recovery). Collazo was also shot, but survived his injuries and served 29 years in prison before returning to Puerto Rico in late 1979 . </P> <P> In 1968, as a result of Robert F. Kennedy's assassination, Congress authorized protection of major presidential and vice presidential candidates and nominees . In 1965 and 1968, Congress also authorized lifetime protection of the spouses of deceased presidents unless they remarry and of the children of former presidents until age 16 . </P> <P> The Secret Service Presidential Protective Division safeguards the President of the United States and his immediate family . They work with other federal, state, and local law enforcement agencies and the military to safeguard the President when he travels in Air Force One, Marine One and by limousine in motorcades . </P>

When did the secret service start protecting presidential candidates