The idea of the American Dream is that anyone has the opportunity to make themselves successful in life. These ideas are embodied in Ragged Dick as he is a poor street boy who with determination and hard work managed to turn himself into a clerk.

A contemporary example of this is The Pursuit of Happiness (2006) - which in relation to 'ragged dick' he is homeless and in order to be successful he works as an intern at a brokerage, he works very hard and eventually gets employed and becomes rich (rags to riches). And so it relates to the idea that if you work hard and are determined you can achieve the American dream.

http://www.youtube.com/watch?v=_xcZTtlGweQ