He graduated from the College of New Jersey (now Princeton University) in 1770, and was the sole instructor at Queen's College, New Brunswick (now Rutgers University) from 1771 to 1774.[2] He studied law and was admitted to the bar in 1774, practicing law in Somerset County, New Jersey.[1]
He married Gertrude Schenck (1753–1794), the daughter of Helena Magdalena Van Liew and Hendrick (Henry) Joahnnes Schenck. Together, they had five children:
Entombed beneath this stone lies the remains of Frederick Frelinghuysen, Esq. Major General of the military forces and representative in the General Assembly of this, his native state. Endowed by nature with superior talents, he was beloved by his country. From his youth he was entrusted with the most important concerns until his death. He never disappointed her hopes. In the bar he was eloquent and in the Senate he was wise, in the field he was brave. Candid, generous and just, he was ardent in his friendships, constant to his friends. The patron and protector of his honorable merit. He gave his hand to the young, his counsel to the middle aged, his support to him that was feeble in years. To perpetuate his memory, his children have raised this monument, a frail memorial of their veneration to his virtues and of their grief and their loss of so excellent a father. He died on the 13th of April 1804, aged 51 years.