The Republic of Indian Stream was a small, unrecognized, constitutional republic in North America, along the section of the US-Canada border that divides the Canadian province of Quebec from the US state of New Hampshire. It existed from July 9, 1832 to 1835. Described as “Indian Stream Territory, so-called” by the United States census-taker in 1830, the area was named for Indian Stream, a small watercourse. It had an organized elected government and constitution, and served about three hundred citizens. (The Free Dictionary)
(Herein is redacted the bulk of the article) but wait, there’s more!
Britain relinquished its claim in January 1836, and American jurisdiction was acknowledged in May 1836. The area was still described as Indian Stream at the time of the 1840 United States Census taken on June 1, 1840; the local population totalled 315. The area was incorporated as Pittsburg in 1840. Pittsburg has 300,000 acres (1,200 km²), of which 282.3 square miles (731 km²) is land area and nine square miles (23 km²) is inland water.
In 1842, the land dispute was definitively resolved by the Webster-Ashburton Treaty, and the land was assigned to New Hampshire. However, the 1845 Lewis Robinson Map of New Hampshire based on the latest authorities, shows the boundary to be north of the town of Clarksville but just south of modern-day Pittsburg.
You really should go and read the whole thing. Wearing a tin-foil tricorn hat, of course!