Ephemerama!

Check out San Francisco collector David Levine's amazing web site of early 20th century travel ephemera.
There are some wonderful examples here of graphic design work from masters such as Herbert Matter, Piet Zwart, and Walter Herdeg (the founder of Graphis magazine). Spend a few hours browsing around!
Graphic Design from the 1920s and 1930s in Travel Ephemera
Shown above: Travel brochure "St. Moritz - Pourquoi St-Moritz Pour Les Sports d'Hiver?" 1936. Photomontages and design by Walter Herdeg and Walter Amstutz. Inside cover.