14. David N. Crosthwait, Jr. (1898-1976)

Notable inventions: Heating systems for huge buildings, vacuum pump, automobile turn signal, and thermostat control

An expert in central air conditioning and heat ventilation systems, Crosthwait took his knowledge of electrical engineering and built everything from vacuum pumps to temperature regulating devices. He would go on to accomplish one of the biggest feats of any 20th century inventor—creating the heating systems for Rockefeller Center and Radio City Music Hall. Someone was in an empire state of mind.