Which important period in american history began in 1929

The Great Depression of America!
It all began with the economic recession in August 1929, but everything got worst on October 24th, 1929: The Black Thursday, or the Crash of Wall Street, Which affected all the world. Then a year later, Banks began to fail. The economy was dead, not only for the united states, but for the whole world. It stayed like that till World war 2 in 1939. 

The great depression started in 1929, I hope that helped.