The phrase “the American Dream” was coined by a Pulitzer prize-winning historian named James Truslow Adams in his 1931 book
The Epic of America. Truslow described the American Dream in this way (pp. 415-416):
But there has been also the American dream, that dream of a land in which life should be better and richer and fuller for every man, with opportunity for each according to his ability or achievement. It is a difficult dream for the European upper classes to interpret adequately, and too many of us ourselves have grown weary and mistrustful of it. It is not a dream of motor cars and high wages merely, but a dream of social order in which each man and each woman shall be able to attain to the fullest stature of which they are innately capable, and be recognized by others for what they are, regardless of the fortuitous circumstances of birth or position. I once had an intelligent young Frenchman as a guest in New York, and after a few days I asked him what struck him most among his new impressions. Without hesitation he replied, "The way that everyone of every sort looks you right in the eye, without a thought if inequality. Some time ago a foreigner who used to do some work for me, and who had picked up a very fair education, occasionally sat and chatted with me in my study after I had finished my work. One day he said that such a relationship was the great difference between America and his homeland. There, he said, "I would do my work and might get a pleasant word, but I could never sit and talk like this. There is a difference there between social grades which cannot be got over. I would not talk to you there as man to man, but as my employer."
No, the American dream that has lured tens of millions of all nations to our shores in the past century has not been a dream of merely material plenty, though that has doubtless counted heavily. It has been much more than that. It has been a dream of being able to grow to fullest development as man and woman, unhampered by the barriers which had slowly been erected by older civilizations, unrepressed by social orders which had developed for the benefit of classes rather than just for the simple human being of any and every class. And that dream has been realized more fully in actual life here than anywhere else, though very imperfectly even among ourselves.
Adams puts this idea of the "American dream" at the center of his description of telling the American narrative and describing what it means to be an American (p. 174):
If Americanism in the above sense has been a dream, it has also been one of the great realities of American life. It has been a moving force as truly as wheat or gold. It is all that has distinguished American from a mere quantitative comparison in wealth or art or letters or power with the nations of old Europe. It is Americanism, and its shrine has been in the heart of the common man. He may not have done much for American culture in its narrower sense, but in its wider meaning it is he who almost alone has fought to hold fast to the American dream. This is what has made the common man a great figure in the American drama. This is the dominant motif in the American epic.
It seems to me that the American dream is sometimes reduced to the idea of upward economic mobility, and while that's certainly part of the vision, it's useful to remember that Adams meant something considerably broader: not just material well-being, but also the opportunity to shape one's destiny; when social order means less and individuals mean more, when social equality is a common presumption in a way that reaches beyond equal treatment before the law, and when the successes and failures of the country are judged by how they affect everyday people.