What happened on 12 April?

15 events from the Ever-When timeline, ranked by how much they mattered.

1. 1861 American Civil War Union versus Confederacy over slavery and federal authority; fighting ends in spring 1865, with an estimated 620,000–750,000 dead.
2. 1204 Sack of Constantinople by Fourth Crusade Three days of looting and slaughter; Byzantine treasures shipped to Venice (the horses of San Marco); Latin Empire installed.
3. 1961 Yuri Gagarin: first human in space Vostok 1 makes Gagarin the first person to orbit the Earth.
4. 1945 Presidency of Harry S. Truman Ended WWII; dropped atomic bombs; Marshall Plan; NATO; Korean War.
5. 1955 Salk polio vaccine Jonas Salk's vaccine begins to eliminate paralytic polio from the wealthy world.
6. 1861 Fort Sumter attacked Confederate bombardment of Fort Sumter begins the Civil War.
7. 1945 Truman becomes US President FDR dies; Truman inherits the presidency in the final months of WW2.
8. 1927 Shanghai massacre Chiang Kai-shek's Nationalists purge their Communist allies, igniting the Chinese Civil War.
9. 1857 Madame Bovary Flaubert's novel of provincial adultery, tried for offending morality.
10. 1981 First Space Shuttle flight Columbia lifts off twenty years to the day after Gagarin — the first reusable orbital spaceplane, flown by humans on its very first launch.
11. 33 Doubting Thomas John 20: "except I shall see in his hands the print of the nails, I will not believe" — eight days later, he does: "My Lord and my God".
12. 1801 Ranjit Singh founds Sikh Empire Ranjit Singh is proclaimed Maharaja in Lahore; by 1813 he has annexed the remaining Sikh misls.
13. 1980 Terry Fox's Marathon of Hope A 21-year-old amputee sets out to run across Canada for cancer research, a marathon a day for 143 days until the cancer returns — his run now repeated yearly in 60 countries.
14. 1954 Oppenheimer security clearance hearing In a closed McCarthy-era hearing, the Atomic Energy Commission dredges up the 'father of the atomic bomb's' left-wing past and his opposition to the H-bomb, and strips him of his s
15. 1827 George Canning's premiership Canning dies after 119 days, the shortest completed premiership until Liz Truss.