Many models of Harley Davidson are collectible due to their rareness, historical significance or engineering uniqueness. An 8-Valve racer made between 1916 and 1923 or an unrestored example of a pre-1910 Single are likely to be worth over $1 million, and a 1909 S-D Twin could fetch $400,000 at auction.
Harley Davidson was founded in 1903 by William S. Harley and Arthur Davidson in Milwaukee. The original motorcycles were pushbikes with engines fitted to them, but the bike considered to be the father of the modern Harley Davidson is the 1936 EL Knucklehead. Around 1,600 of these bikes were produced, and they are worth as much as $100,000 to collectors.
Some models of Harley Davidson are considered especially desirable if unmodified from their original specifications. The Second World War era WLA Liberator was often transformed for civilian use after the war, making original olive green models with gun scabbards quite rare and collectible. Similarly, the Sportster XLH usually had its boat-tail fibreglass rear end chopped off in the 1970s, so a complete example is now both uncommon and valuable.
Over 70 different models of motorcycle have been sold under the Harley Davidson banner since 1903, and some are far more collectible than others. Groups such as the Antique Motorcycle Club of America or the staff at the Harley Davidson Museum have a wealth of experience collecting such bikes and are often willing to share their knowledge.