What happened on 1 May?

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

1. 1707 Acts of Union 1707 Parliaments of England and Scotland merge to form the Kingdom of Great Britain.
2. 1851 Great Exhibition at the Crystal Palace Showcase of industry and empire in Hyde Park; symbol of the Victorian high tide.
3. 1786 Mozart's The Marriage of Figaro premieres Comic opera based on Beaumarchais's play that the censors had banned.
4. 1781 Kant's Critique of Pure Reason Kant's revolution in epistemology - synthetic a priori judgments - foundational to modern philosophy.
5. 1941 Citizen Kane Orson Welles's debut feature, regularly named the greatest film ever made.
6. 1931 Empire State Building New York skyscraper that defined the Manhattan skyline for forty years.
7. 1849 Thoreau's Civil Disobedience Essay arguing the duty to disobey unjust government.
8. 1876 Victoria becomes Empress of India Royal Titles Act adds 'Empress of India' to Victoria's titles; Disraeli's flourish marks high tide of imperial monarchy.
9. 2004 EU eastern enlargement Ten states — eight of them former communist — join the European Union in its biggest single expansion; Romania and Bulgaria follow in 2007, Croatia in 2013.
10. 2004 EU eastward enlargement Ten mostly former-Communist countries join the European Union.
11. 1756 The Diplomatic Revolution Europe's alliances flip overnight: Austria, hunting revenge for Silesia, allies with its ancient enemy France, and Britain signs with Prussia — the reversal sealed by the Treaty of
12. 1956 Hundred Flowers Campaign Brief CCP encouragement of criticism, soon reversed into the Anti-Rightist purge.
13. 1845 Douglass's Narrative published The Narrative of the Life of Frederick Douglass names names and places, demolishing the claim that no former slave could have written it.
14. 305 Diocletian abdicates Unique abdication of a Roman emperor; Diocletian retires to his palace at Spalatum (Split) to grow cabbages.
15. 1862 Parkesine — first man-made plastic Alexander Parkes exhibits Parkesine (nitrocellulose-based) at the Great London Exposition; first plastic material, ancestor of celluloid.