William Ellery was born in Newport, Rhode Island on December 2, 1727, the second son of william Ellery, Sr. and Elizabeth Almy, a descendant of Thomas Cornell. He received his early education from his father, a merchant and Harvard College graduate. He graduated from Harvard College in 1747, where he excelled in Greek and Latin. He then returned to Newport where he worked first as a merchant, next as a customs collector, and then as Clerk of the Rhode Island General Assembly. He started practicing law in 1770 at the age of 43 and became active in the Rhode Island Sons of Liberty.