After World War 1 ended in 1918 there were a lot of ex-military pilots in the United States who wanted to keep doing what they loved-- soaring among the clouds.
Fortunately for those pilots there were also a lot of airplanes that were surplus to the needs of the military, and they were for sale cheap. Most were training aircraft, like the Curtiss Jenny and Standard J-1, and these machines became the backbone of what was called barnstorming, after the travelling theater troupes of the 19th Century.
While some pilots found work flying in Hollywood for the movies, and some flew for the Air Mail, most bought a surplus Curtiss or Standard for a few hundred dollars, and set out to sell aviation to the masses.
The barnstormers did a lot of crazy things to attract customers-- wing walking, car to plane transfers using rope ladders, and various other spectacular stunts. By the mid-1920s the Civil Aviation Administration was born to regulate aviation and make it more safe