Several contributors have mentioned relatively late textbooks, such as 
Branson's, when Warren Young has already pointed out the example of 
Meade's 1936 textbook, which had a 1938 U.S. edition.  If one wants a 
popular U.S. textbook, Hansen's "Monetary Theory and Fiscal Policy" 
(1949) gives an IS-LM analysis.  Samuelson's "Economics," 3rd edition 
(1955) popularized the "Hicks-Hansen" IS-LM model, although he relegated 
it to an appendix.

Kevin Hoover