How did the democratic-republic form of government develop?

This week, 215 years ago, the lofty ideals of the Constitution passed their first test. The dawn of American democracy didn't come in 1776, with the Declaration of Independence. It didn't come in 1788, when the Constitution was ratified by the states, or in 1789, when George Washington took office.

In the US, the notion that a republic was a form of democracy was common from the time of its founding, and the concepts associated with representative democracy (and hence with a democratic republic) are suggested by John Adams (writing in 1784):

No determinations are carried, it is true, in a simple representative democracy, but by consent of the majority or their representatives.