Cornelius Hopper, son of Matthew (Mathias/Matheus) Hopper and Aeltje Kuyper was born either February 8, 1756 (per the baptismal record) or February 14, 1756 (Bible record). He was born either in or near Clarkstown, Rockland County, New York. He was baptized in the Clarkstown Reformed Dutch Church on February 29, 1756. Cornelius married Hanna Rockwell on December 25, 1777. They had 12 children: Matthew (1778-1779), Hannah (1780-1842), Olive (1781-1862), Esther (1784-1855), Mary (1787-1854), Anna (1789-?), Rockwell (1792-1875), Amy (1794-1859), Margaret* (1797-1860, our direct ancestor), Ira (1799-1861), Elizabeth (1801-1887), and Sally (1804-1889)
He served as a private in the New York 4th Orange County Militia, commanded by Major John Halthorn. Records in the National Archive show that Cornelius was paid 14 shillings, 2-1/2 pence for 8 days of service at Fort Montgomery.