My vote would be for Benjamin Franklin. He was instrumental in building a set of colonies that were mature enough for self-governance (with libraries, schools, colleges, newspapers, industry, fire departments and postal service). The Declaration of Independence might never have been written or passed without his political choreography, which might not have occured if Parliament hadn't so personally humiliated him when he served as a lobbyist the Commonwealth of Massachusetts a few years earlier. The War of Independence would not have been won without his diplomacy on our behalf.
Plus he was America's most famous scientists, most famous inventor, and most famous satirist of the 18th Century. Not bad for a fellow who never served as president. It's all about the Benjamins ...