You may not have realized it before, but you really need this graphic in your life. Jishai Evers of Dadaviz created this map of what people in various states call themselves using the U.S. Government Printing Office style manual.
For most states, you’re safe adding an –n, and maybe a few other letters, to the state’s name – a la Coloradans, Nebraskans and Californians. For three states, Wyoming, Wisconsin and New Hampshire, the correct method is to add an –ite. For a handful of states in the northeast, the style is to add an “r” – New Yorker, Vermonter, Mainer, Marylander, Connecticuter and Rhode Islander.