WordNet sense 1 (an American who lives in the North (especially during the American Civil War)):

northerner, yank

WordNet sense 2 (an American who lives in New England):

New Englander

WordNet sense 3 (an American (especially to non-Americans)):

Yankee-Doodle

WordNet sense 4 (in or characteristic of a region of the United States north of (approximately) the Mason-Dixon line):

northern