[265][266] He visited the cottage at Dunganstown, near New Ross, County Wexford, where his ancestors had lived before emigrating to America.[267]
Kennedy also was the first foreign leader to address the Houses of the Oireachtas, the Irish parliament.[266][268][269][270]
Kennedy later told aides that the trip was the best four days of his life.[271]

Nuclear Test Ban Treaty
Main article: Partial Nuclear Test Ban Treaty
Kennedy signs the Partial Test Ban Treaty, a major milestone in early nuclear disarmament
Troubled by the long-term dangers of radioactive contamination and nuclear weapons proliferation, Kennedy and Khrushchev agreed to negotiate a nuclear test ban treaty, originally conceived in Adlai Stevenson's 1956 presidential campaign.[272] In their Vienna summit meeting in June 1961, Khrushchev and Kennedy both reached an informal understanding against nuclear testing, but the Soviet Union began testing nuclear weapons that September. In response, the United States conducted tests five days later.[273] Shortly afterwards, new U.S. satellites began delivering images that made it clear that the Soviets were substantially behind the U.S. in the arms race.