Jean Hugard was the first to publish a method for folding a single bill to look like two bills; see his Money Magic, 1937, p. 57. Hugard assigns no credit for the fold or its magical use.
Three years later, Jack Vosburgh published another method of folding a bill to look like two; The Jinx, No. 122, Dec. 1940, p. 711. Vosburgh makes the credible statement that the fold he describes was originally employed by shortchangers, leading to the surmise that Hugard may have described another method from that profession.
Sam Berland published another variation of the fold, c. 1940, in Samuel Berland's Billtrix, Series No. 1. His fold was included by Martin Gardner in Over the Coffee Cups, 1949, p. 5.
In 1949, Orville Meyer published yet another folding method to make one bill appear to be two; Hugard's Magic Monthly, Vol. 6 No. 11, Apr. 1949, p. 530.
In 1989, Karl Fulves published an embellishment for the one-as-two bill fold. The number from the corner of a five-dollar bill is stuck over one corner of a one-dollar bill folded to look like two bills. This false number is later secretly removed so that, when the bill is unfolded, a five-dollar bill seems to have vanished. See “Safe Deposit” in Fulves's Self-Working Coin Magic, 1989, p. 80.