In 1960, Sills and her family moved to Milton, Massachusetts, near Boston. In 1962, Sills sang the title role in Massenet's "Manon" with the Opera Company of Boston, the first of many roles for opera director Sarah Caldwell. Manon continued to be one of Sills' signature roles throughout most of her career. In January 1964, she sang her first Queen of the Night in Mozart's "The Magic Flute" for Caldwell. Although Sills drew critical praise for her coloratura technique and for her performance, she was not fond of the latter role; she observed that she often passed the time between the two arias and the finale addressing holiday cards.