According to the study, what did john steinbeck do to prepare for his book the grapes of the wrath?

John Steinback wrote the Noble-prize literature (1940)  for five months. While doing so, this was the time when his brother-in-law just died and his fears and insecurities on the upcoming war that might affect their house in California. In short, John was under a lot of stress and problems during the creation of the book. However, he still deed his efforts such as visiting the  Arvin Federal Government Camp to get a picture of the place he could use in his book.