Personal automobile – One of the most popular attractions of the Exposition was contained in the Palace of Transportation: automobiles and motor cars. The automobile display contained 140 models including ones powered by gasoline, steam, and electricity. The private automobile first made its public debut at the Louisiana Purchase Exposition. Four years after the Louisiana Purchase Exposition, the Ford Motor Company began producing the Ford Model T making the personal automobile more affordable. Since that time, the automobile has increased in popularity, advanced in technology, and expanded the mobility of humanity. A prototype car radio was also demonstrated by inventor Lee de Forest.