In 1794, he was appointed Health Officer of the Port of Albany In February 1804, Cooper attended a dinner party during which
Alexander Hamilton spoke forcefully and eloquently against the
Federalists' plan to nominate
Aaron Burr as their candidate for
Governor of New York. Cooper later wrote a letter to
Philip Schuyler, Alexander Hamilton's father-in-law, in which he made reference to the "despicable opinion" Hamilton had expressed about Burr. The letter was published in
The Albany Register, but was tame compared to other attacks on Burr in the press. Still, Cooper's letter proved the last straw in the ongoing rivalry between Burr and Hamilton. When Burr read the letter weeks later, shortly after his
defeat in the governor's race, he was enraged by Hamilton's alleged remarks, and challenged
Hamilton to a duel, in which Hamilton was killed. From March 1806 to June 1807, Cooper was First Judge of the
Albany County Court. From 1815 to 1816, he was a member of the
Erie Canal Commission. In April 1817, while his father-in-law was Acting Governor, Cooper was appointed
Secretary of State of New York. ==Personal life==