What are the allegories?

Herbert Hoover serves as an allegory of difficult times, “a Great Depression.” It “swept over the nation,” and even the kids, Joey and Mary Alice, could see that. The whole country “couldn’t seem to throw it off,” “it was still Hoovering over” all of them. They could see “hard times from the window of the Wabash Blue Bird.” The “freight” trains were loaded down “with men trying to get from one part of the country to another, looking for work and something to eat.”