Born in Charleston, South Carolina to Martin Luther Hurlbut and Lydia Bunce. His father was a Unitarian minister and educator. Hurlbut studied law with James L. Petigru as his mentor, worked for him as a law clerk, and was admitted to the South Carolina Bar in 1837. During the Second Seminole War, he served as adjutant of a South Carolina infantry regiment. In 1845, Hurlbut relocated to Illinois, where he established a law practice in Belvidere. He started his own family in 1847 after marrying Sophronia R. Stevens; she gave birth to two of his children.