In 1821, Missouri's Boone's Lick Trail became the first section of what would later be the famous Santa Fe Trail, opening up trade routes to the southwest. 

In 1923, the Hollywood sign was originally erected as "Hollywoodland" to promote a real estate development. It wasn't intended to be permanent.

In 1896, the shortest war in history was fought between Britain and Zanzibar. It lasted only 38 minutes.

In 1783, a volcanic eruption in Iceland led to a famine that killed almost a quarter of the country's population and had climate effects across Europe.

In 1958, a small nuclear reactor in Virginia was used to power the first nuclear-powered commercial ship, the NS Savannah, which was part of Eisenhower's "Atoms for Peace" initiative.

In 1904, the first underground line of the New York City Subway opened, changing urban transit forever.