The early history of Isaac is unknown, except for the fact that the Shepard family moved from Connecticut to New York State. Isaac married Sarah Lackore on July 25, 1825 in Champion, New York. After their marriage, the Shepard family moved across the state of New York.
On March 17, 1834, the Shepard family joined the Church of Jesus Christ of Latter-day Saints. They soon moved from New York and joined the Saints in Ohio and Illinois.
During this time, Sarah died on May 7, 1847. Soon after, Isaac married Eleanor Jane Davis on Feb 1, 1848. The exact company the Shepard family joined to cross the plains is unknown. They arrived in the Salt Lake Valley in 1848.
After their arrival, the Shepard family moved to Farmington, Utah. Isaac and his children settled near a canyon and began working on gathering lumber. In 1859, the Shepard family moved to Richmond.