The Civil War began. (1861) Confederate forces fired on the Fort Sumter, a Union-held fort in Charleston, South Carolina, bringing long-standing tensions to a head and starting the Civil War. Though most people on both sides were confident the war would end within a year, it lasted through 1865, with more fatalities than any other American war.
The polio vaccine was declared safe. (1955) Though rare in developed countries now, polio was a major killer before the Salk polio vaccine went into use in the 1950s — in fact, more children died from polio than any other communicable disease in the 1950s. When the vaccine was declared safe, massive immunization campaigns went into effect, and the disease was virtually eradicated in America.
Yuri Gagarin became the first man in space. (1961) Russian Cosmonaut Gagarin was made into an overnight celebrity when he became the first man in space, as well as the first man to orbit the Earth on this day. His flight was a major blow to the US, and sparked even greater efforts to win the space race.
Bill Haley and the Comets recorded Rock Around the Clock. (1954) Often called the first rock and roll record, Rock Around the Clock became sensationally popular after it was used as the opening song in Blackboard Jungle, and sold more than 1 million records in one month in 1955 alone.
President Franklin Roosevelt died. (1945) Roosevelt died while on vacation, leaving Truman to take over. Though sometimes controversial, he had brought America through the Great Depression and World War II, and was one of the most influential presidents.
The Mark Strand Theatre opened. (1914) The theater was the first "movie palace," a huge luxurious movie theater almost like an opera house. Patrons could watch from balcony seats, socialize in the rotunda during intermissions, and were even sometimes given live orchestra performances before and after movies.
The Townshend Act was repealed. (1770) The British-mandated Townshend Act placed import taxes on many profitable goods like paper, glass, and tea. The act led to mass riots and eventually the Boston Massacre before it was repealed.
Galileo was convicted of heresy. (1633) Foundational scientist and astronomer Galileo was convicted of heresy because he refused to recant his statement that the Earth revolved around the sun, instead of vice versa. He spent the rest of his life under house arrest.
The Fort Pillow massacre occurred. (1864) Confederate troops led by Nathan Bedford Forrest sacked a Union garrison at Fort Pillow, which was largely manned by African-American troops. There were huge numbers of Union fatalities, which led some to claim that the Confederate troops had deliberately massacred them.
The first space shuttle was launched. (1981) The Columbia,the first reusable manned spacecraft, was launched for the first time on this day. It was a major step forward for NASA, and was eventually used to help build the International Space Station.