So I was trying to think of the most famous writers I could from each state. A few were obvious (Cather, Faulkner, Toole). Still, I didn't come up with too many--it turns out I'm not actually sure where most writers are from. I put the name in italics if I've never read a book by the author.
California--John Steinbeck? Jack London? Charles Bukowski? Raymond Chandler?
Colorado--Hunter S. Thompson?
Louisiana--John Kennedy Toole
Massachusetts--Melville? Nathaniel Hawthorne? (no, I never made it through The Scarlet Letter), Henry David Thoreau, Ralph Waldo Emerson, oh, I've got a recent one--Robert Parker (the Spenser mysteries)
Mississippi--William Faulkner, Eudora Welty (I think)
New Jersey--Junot Diaz (Oscar Wao was set there, I assume he's from there)
New York--Walt Whitman (Ok, he's more of a poet, but he's who I came up with), Langston Hughes? Ralph Ellison? (obviously they lived in Harlem, but were they from there?), Stan Lee (!), about a million others who lived in NY but weren't from there
North Carolina--David Sedaris
Ohio--Harriet Beacher Stowe (I think), P.J. O'Rourke, Harvey Pekar
Oklahoma--S. E. Hinton (Lee told me this one, and how great is it that OK's most famous author is YA?)
Pennsylvania--John Updike (aren't his books set in suburban Philadelphia?)
Virginia--Edgar Allan Poe (I know Baltimore claims him but I think he was from Richmond originally)
Washington State--Frank Herbert
Leave any others you know in the comments and I'll add them to the list.