Landon was born Eugene Maurice Orowitz on October 31, 1936 in Forest Hills, a neighborhood of Queens, New York. His parents were Peggy (née O'Neill; a dancer and comedian) and Eli Maurice Orowitz. His father was Jewish, and his mother was Roman Catholic. Eugene was the Orowitz family's second child; their daughter, Evelyn, was born three years earlier, in 1933. In 1941, when Landon was four years old, he and his family moved to the suburb of Collingswood, New Jersey, near Philadelphia. He attended and celebrated his Bar Mitzvah at Temple Beth Shalom. His family recalls that Landon "went through a lot of hassle studying for the big event, which included bicycling to a nearby town every day in order to learn how to read Hebrew and recite prayers."