The Joad family is forced to leave their tenant farm in Sallisaw, Oklahoma, at the beginning of The Grapes of Wrath by John Steinbeck. Things are hard during the Great Depression, especially for those living in the Dust Bowl; the Joads and thousands of others are forced to leave their land and have great hope that they will be able to enjoy a life of prosperity once they reach California.
The Joads' journey follows a new road, Route 66,
the main migrant road . . . the long concrete path across the country . . . the path of a people in flight, refugees from dust and shrinking land, from the thunder of tractors, and shrinking ownership. . . . 66 is the mother road, the road of flight.
The major stops along their route are well documented in the googlemaps link (below) and include the cities of Padan, Oklahoma City, and Bethany in Oklahoma. The last major city to be mentioned is before they arrive in California is Santa Rosa, New Mexico; however, the Joads (and others) must cross the Mojave Desert and the Colorado River before they arrive in what they think will be their Promised Land.
Once they arrive in California, the Joads move from Needles to Daggett to Tehachapi, then move on to Bakersfield. So many of the other places they live do not have any official names because they are not official cities.
It is a daunting drive to think about taking in the 1930s; add to that strains of heat and weight on the vehicles and it is shocking that so many of the "okies" even made it to California at all--and undoubtedly, many of those who made it wished they had not.