William Collier, thought to be a brewer in London, was one of the Merchant Adventurers who financed the Mayflower company of Pilgrims. Mr. Collier's name appears frequently in correspondence between the Pilgrims in New Plymouth and their backers in London. He was one of the signers of the agreement where, on 26 October 1626, the Pilgrims bought out all rights of the London company of Adventurers for 1800 pounds, to be paid in installmenets of 200 pounds per year.

In 1633, William Collier and his family came to Plymouth Colony in the ship Mary and Jane. He at once took a prominent position in the colony and was reported to be the wealthiest man there. He was appointed one of the assessors in 1634 and he himself was taxed 2 pounds 5 shillings, the highest tax in the colony. He was one of the first settlers of Duxbury, which was established in 1637.

He was made a freeman on 1 January 1633/4. He was on many committees: assigning and laying out land, building a meeting house, laying out highways, and revising the laws. He served on the Council of Wars for four years. He was assistant governor for twenty-eight years and a member of the Provincial Congress in 1643. He was also one of a committee of two appointed by the Congress to sign the Articles of Confederation. In 1659, "on account of his age and much business on him, the court ordered the treasurer to procure for him a servant and allowed 10 pounds for that purpose."

William and his wife Jane (Clark) Collier had at least twelve children, eight of whom died in England (Robert S. Wakefield, More on the Children of William Collier, TAG 49:215 and 51:58). They did bring four daughters with them to America:

• Rebecca, b. ca. 1611; m. 15 March or May 1634, Daniel Cole.
• Sarah, b. ca. 1612; m. (1) 15 March of May 1634, Love Brewster; m. (2) ca. 1652, Richard Parke.
• Mary, b. ca. 1614; m. in 1635, Gov. Thomas Prence, as his second wife.
• Elizabeth, b. ca. 1616; m. in 1637, Constant Southworth.