German mathematician Carl Friedrich Gauss constructed the first heptadecagon using a ruler and a compass.
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The US adopted the 15th Amendment, guaranteeing citizens the right to vote.
North Carolina repealed its controversial bathroom law that restricted transgender use.
The United States bought Alaska from the Russian Empire.
The Heinkel He 100 fighter set a world airspeed record of 463 mph (745 km/h).
Swimmer Michael Phelps smashed the world record for the 200-meter butterfly swim at just 15 years old.
