For five years, he was known as the leader of the Free World. But for the first several years of his life, Richard Milhous Nixon had a more modest title: farm boy. Wednesday will mark the date, 100 years ago, of a winter day so cold that Hannah Nixon was advised it would be better to bear her fifth son at home than risk traveling in the chill to a hospital. That was the day a small, kit-constructed home surrounded by citrus trees saw the birth of the man who would become the 37th president of the United States.