The early part of the 1920s was a time of economic boom for the United States. Their industries had supplied the war in Europe, generating enormous profits. The automobile industry and those related to it, such as the oil companies, were expanding very rapidly.
In The Great Gatsby, we are told that Tom Buchanan had bought his palatial mansion from an "oil man".
In the novel, cars play a prominent part:
Railroads (railways) and aviation were also thriving: we are told Gatsby has a 'hydroplane', a plane which can take off and land on water.
This economic expansion led to a rise in consumerism and this materialistic attitude is satirised in the character of Myrtle in The Great Gatsby:
I'm going to give you this dress as soon as I'm through with it. I've got to get another one tomorrow. I'm going to make a list of all the things I've got to get.
However, other parts of the economy were in decline, particularly agriculture. Increased mechanisation in farming had led to land being over intensively worked, and this, coupled with a prolonged period of drought, led to severe soil erosion problems in certain Midwestern states. This area of the country came to be known as the 'Dustbowl'.
One of the states affected would have been North Dakota, where we are told Gatsby's parents were "unsuccessful farm people". John Steinbeck also deals with this issue in his novel 'The Grapes of Wrath'.
In addition, workers on the lower rungs of the ladder did not share in the prosperity. George Wilson struggles to make a living, and the "ash-grey" men who "swarm" to unload the railroad cars also seem to have missed out on the general bonanza.