Vermont was once an independent republic.
Not everyone wanted to be part of the United States when the Revolutionary War broke out. Vermont, for instance, declared itself an independent republic from 1777 to 1791, due in part to ongoing disputes with neighboring New York, which claimed the land as its own. The future Green Mountain State adopted its own constitution and operated as a de facto independent country. After briefly being called New Connecticut, the region eventually settled on the name State of Vermont, but was also known as the Vermont Republic. In addition to having its own currency and postal service, Vermont also abolished slavery on July 2, 1777 — the first American colony to do so. (Vermont at one point toyed with the idea of joining the Province of Quebec in the early 1780s before ultimately deciding against it.)
Though the Vermont Republic wasn’t officially recognized by the U.S., it was largely left to its own devices. No less an authority than George Washington advised against military action in 1783, in part because the country was “very mountainous” and its citizens were “a hardy race, composed of that kind of people who are best calculated for soldiers.” Vermont eventually settled its differences with New York and voted to ratify the U.S. Constitution in 1791, officially joining the new nation.