William Trevore was hired by the Pilgrims to be a laborer for a year, and probably to be a seaman on the Speedwell prior to the decision to leave it behind. Trevore is reported to have accompanied Myles Standish on the first trip by the colonists to Boston Harbor, where an island near Dorchester was named the "Isle Trevore." It later became known as Thompson's Island.
After completing his year of service, William Trevore returned to England onboard the Fortune in December 1621. On the return voyage, the Fortune was intercepted by French privateers under direction from the Marquis de Cera, and the crew and passengers were held prisoner on the Ile d'Yeu, Poitou for a period of time before being released.
In 1623, Robert Cushman (one of the Pilgrims' business coordinators back in England) wrote a letter stating that "William Trevore hath lavishly told [Thomas Weston] but what he knew or imagined of Capawack, Mohegan and the Narragansetts." He later became master of a ship called the William, and made several trips delivering passengers to America during the 1630s. In 1650, he signed a couple of depositions regarding Thompson's Island.