William Henderson founded Ace Motor Corporation in 1919 and acted as chief engineer/designer. Henderson previously owned Henderson Motorcycle Company, known for their large and fast motorcycles. After selling the company to Schwinn, William Henderson became dissatisfied with the new ownership and left to form Ace Motor Corporation, where he returned to his philosophy of light and fast motorcycles. Throughout its run, Ace built 4-cylinder motorcycles, with only slight variations between models.
In a sad twist of fate, William Henderson was killed in 1923 by a speeding car that struck him while he was driving that year's new Ace model to a promotional photo shoot. Art Lemon, Henderson's former assistant at Henderson-Excelsior, took over as Ace's chief engineer. Ace management requested that Lemon build the fastest motorcycle in the world, and gave him permission to purchase a Sprag Dynamometer to test engine output. In 1923 Lemon built the XP3 and XP4. Both models broke speed records.
In 1927, Indian Motorcycle Company purchased Ace Motor Corporation. For one year, they built the Indian Ace, but then the Ace name was discontinued.