When did the book The Grapes of Wrath take place?

The setting of the novel changes drastically as the novel progresses. It begins in Oklahoma during the Dust Bowl years of the late 1930’s, and the first half of the novel then follows the Joads across the Midwest and West into California. Most of the latter half of the book is set in Hoovervilles and the Weedpatch government camp in central California. As the setting changes from barren, overworked fields in Oklahoma to luscious orchards in California, the plight of the Joads goes the opposite way. The Promised Land in California is cut off to them by the greedy farm owners who repress the farmers.