He was baptized in Colnbrook, Horton, Co. Buckinghamshire on Oct 12, 1628, the son of Joseph Jenckes (also spelled Jenks, Jencks) and his first wife Joan Hearne Jenckes.
Joseph Jenckes II is known as the founder of Pawtucket. A skilled ironworker, he had come to the New World to join his father, Joseph Jencks I, who had organized and operated the first American iron works in Saugus, MA. In 1670, Joseph II left Massachusetts, intending to build his own forge in Rhode Island. On October 10, 1671, he purchased 60 acres of land on the west bank of the Blackstone River, marking the establishment of the first permanent settlement of Pawtucket. However, it was short-lived, as the Jenckes settlement was burned to the ground in 1675 during King Philip's War. When the war ended, the Jenckes forge was rebuilt, and soon it became the center of a small village including the foundry, a gristmill, and sawmill. The commerce of the village was founded on the production of iron products essential to the survival of these early settlers.
Joseph Jenckes was admitted a freeman in 1677, and served several terms in the Rhode Island Assembly between 1679 and 1698. During 1685–1688, at the direction of King James II, Rhode Island became a county in the Dominion of New England, under Governor Sir Edmund Andros. After the Revolution of 1688, King William and Queen Mary ascended to the throne, and Joseph Jenckes was included in a small group selected to write a letter congratulating them on their ascension and informing them that Sir Edmund Andros had been arrested in Rhode Island.
About 1652 or 1653, he married Esther Ballard, in Lynn, Essex Co, MA.