Mapbacks extend from #5 to at least #550; then maps became less of a fixed feature of the books and disappeared entirely in 1951. (Numbers 1 through 4 had no map, although a later re-publication of #4, The American Gun Mystery by Ellery Queen, added a map.) The occasional number in the series between #5 and #550 contains no map, but some sort of full-page graphic or text connected with the book's