German mathematician Carl Friedrich Gauss constructed the first heptadecagon using a ruler and a compass.
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Swimmer Michael Phelps smashed the world record for the 200-meter butterfly swim at just 15 years old.
The United States bought Alaska from the Russian Empire.
Ether was used as an anesthetic for the first time, by American surgeon Crawford Long, in Athens, Georgia.
North Carolina repealed its controversial bathroom law that restricted transgender use.
The US adopted the 15th Amendment, guaranteeing citizens the right to vote.
