Hilary was born in Lincoln, Nebraska, to Judith Kay (Clough), a secretary, and Stephen Michael Swank, who served in the National Guard and was also a traveling salesman. Her maternal grandmother, Frances Martha Dominguez, was of Mexican descent, and her other roots include German, English, and Scottish. During her early childhood, her family moved to Spokane, Washington, and when she was six, to Bellingham, Washington.
Hilary was discovered as a child by producer Suzy Sachs, who coached her in acting. When she was nine years old, she starred in her first play as "Mowgli" in "The Jungle Book". She began to appear regularly in local theater and school plays. She went to school in Bellingham, where she lived with her family, until she was 16. She competed in the Junior Olympics and Washington State championships in swimming; she ranked 5th in the state in all-around gymnastics (which would come in handy for starring in The Next Karate Kid (1994) years later). In 1990, Hilary and her moth