Assembly line production made cars cheap enough for the masses in the early 1900s, but it took a separate set of innovations to convince people to ditch their horse-drawn carriages for internal-combustion vehicles. One important innovation allowed motorists to start their engines without standing outside and turning metal cranks protruding from the fronts of their cars.

Crank starting was not only an inconvenient and laborious task but one that occasionally had nasty consequences. An engine misfire could cause the metal arm to jerk violently, sometimes causing sprains and broken bones. Henry Leland, president of Cadillac, knew firsthand the dangers; a friend of his was struck in the face by a wayward crank and died in the hospital from complications related to a broken jaw. The accident convinced Leland to pursue inventor Charles Kettering’s proposal for an electric starter in 1910.

Kettering began his career in 1904 at National Cash Register in Dayton, OH, where he developed, among other things, an electric cash register that did away with the hand crank for cashiers. He left the company five years later to form his own inventing firm. It was during this time that he figured out a method for electric starting. The basic idea had been kicked around for more than a decade, but most engineers had concluded that a motor and battery powerful enough to spin the crankshaft would have to be nearly as large as the engine they were meant to start. Kettering, however, recalled a crucial insight from his NCR days: the motor needed to provide only a brief burst of power, turning just long enough to ring up a sale, or in this case, to turn over the engine. The hardware could be small because it would not be operating continuously.

Kettering and his assistants went to work designing their starter mechanism in the fall of 1910. By Christmas, they were testing a starter motor about a cubic foot in size. Cadillac soon agreed to include electric starters in its 1912 model. By 1920, when Kettering sold his research operation to Cadillac’s parent General Motors, nearly every new car featured an electric-starter option. Kettering went on to direct GM’s research for 27 years.