Glenn H. Curtiss (1878-1930), an early member of the SAE, was one of America's premier aviation pioneers, a self-taught engineer, and creator of a broad series of commercially successful engines for both aviation and motorcycles. Best known for his aerial accomplishments (from the 1908 June Bug to World War I aircraft, such as the JN-4 Jenny trainer), Curtiss developed solid experience with engines long before (dating back to 1901). His early interest in bicycle racing led to motorcycling and his motorcycle engines evolved into aero engines-first for airships, then aeroplanes. Curtiss engines of this era (the most familiar are his V-8 4-stroke water-cooled designs) were noted for advanced construction materials, lighter-than-average weight, reasonable reliability and some innovative mechanical features. Curtiss engines were not the most radical or advanced examples of the art, but were sufficiently respected and built well enough to capture the majority of the early U.S. aircraft engine business to the WWI era and slightly beyond.Much has already been written about Curtiss and his aircraft work but much less has appeared on his distinguished engines. Accordingly, this paper will address early Curtiss engines from 1901 to 1918, after which the inventor was largely disengaged from the business. The piston aircraft engine enterprise founded by Curtiss continued on, merged with Wright in 1929, and finally ceased production in the early 1960s.