Plattsburgh, city (1990 pop. 21,255), seat of Clinton co., NE N.Y., on Lake Champlain; settled 1767, inc. 1902. It is a trade and distribution point, with plants making transportation equipment, paper, and plastics. The city is also a summer vacation center, attracting Canadians as well as Americans. During the War of 1812 a makeshift American fleet under Thomas Macdonough defeated the British in a pitched battle on Lake Champlain near Plattsburgh, compelling an accompanying land-invasion force under Sir George Prevost to return to Canada. The State Univ. of New York College at Plattsburgh is in the city.