William Clarke was born in Boston on April 9, 1732, the eldest recorded child of Richard Clarke and Elizabeth Winslow Clarke. His parents married in 1733 according to the family-history summary, creating a possible chronological inconsistency between the recorded birth and marriage dates; the surviving compilation nevertheless identifies William as their eldest son. His father, a Harvard graduate, became one of Boston’s most successful import merchants, while his mother belonged to the prominent Winslow family.

William grew up as the first of twelve Clarke children. His younger siblings included Hannah, Elizabeth, Edward, Joseph Lee, Mary, Jonathan, Susanna, Isaac Winslow, Sarah, Lucy, and Richard. Their household was shaped by Atlantic commerce. Richard Clarke dealt in tea, sugar, molasses, oil, potash, and other goods moving between Boston, London, Canada, the West Indies, and neighboring ports. As the eldest son, William would have encountered account books, letters, invoices, shipping intelligence, and the social obligations of a prosperous mercantile family from an early age.

He received the classical preparation necessary for Harvard College and graduated with the class of 1752. Harvard’s curriculum emphasized Latin and Greek, logic, rhetoric, mathematics, natural philosophy, ethics, and theology. College trained young men for the ministry, law, medicine, commerce, or public life and also connected William to a network of educated New England families. The available family records do not identify a later professional degree or a clearly defined independent career.

After Harvard, William returned to the world of his family. His father’s firm was expanding, but the surviving business collection more clearly documents the later participation of William’s brothers Edward, Jonathan, and Isaac. William never lived to see the partnership become notorious in the tea crisis. He died at his father’s Boston home on January 27, 1761, at twenty-eight.