The most important development was the democratization of the United States. At the time of the Revolution and soon after, America was still fairly hierarchical with an acknowledged elite. The elites were the ones who ran for public office and only the relatively well-off were allowed to vote.
As decades passed, America became more democratic and egalitarian. The frontiers of the country expanded and more and more of the population became independent small farmers who did not feel they were below anyone in the social hierarchy. As America became more of a frontier country full of small farmers, it became more democratic. Andrew Jackson was the epitome of all of these developments. He was from a frontier family that was very much outside of the elite. He was a self-made man like many of the people on the frontier. Because of this, he was a great symbol of his times and was very appealing to many Americans.