Ken Schenck has some interesting thoughts on the origin of evangelicalism and how the concept has changed over time.
The origins of American evangelicalism are in these preachers of assurance, these preachers that you can be justified by faith now and you can know it. In short, the original evangelicals in America were revivalists. George Whitfield and the First Great Awakening are the starting point for American evangelicalism and, yes, Jonathan Edwards was a part of that.
John Wesley and his followers are a key part of that, the early American Methodists like Francis Asbury and Thomas Coke, Then the Cane revivals in the early 1800s, the Second Great Awakening, are part of that. Think of the Baptists who preached assurance and a moment of conversion.