Casparus Dieterich Weiberg was born in Westphalia, Germany. He studied at Duisburg and was ordained before coming to America in 1762 or 1763. In 1763, he was briefly a clergyman in the German Reformed (or Calvinist) Church in Easton, Pennsylvania, also serving churches in Pennsylvania’s Berks and Northampton Counties and Warren County, New Jersey. The following year he moved to Philadelphia where he served as minister of the First and Second German Reformed Churches until his death.
During the American Revolution, Weiberg was reportedly imprisoned for his patriotic stand and served as a chaplain in the Continental Army.
In addition to his honorary degree from Penn, Weiberg was awarded an honorary Doctor of Divinity degree by Princeton in 1787 for his role in the 1787 founding of Franklin College. As the senior minister of the German Calvinist Church in Philadelphia, Weiberg served from 1779 until his death in 1790 in an ex officio capacity as a trustee of the University of the State of Pennsylvania (now the University of Pennsylvania).