Editing 1871 (section)

=== April–June ===
* [[April]] – The [[Stockholms Handelsbank]] is founded.
* [[April 4]] – The New Jersey Detective Agency is chartered, and the [[New Jersey State Detectives]] are initiated.
* [[April 10]] – In [[Brooklyn, New York]], [[P. T. Barnum]] opens his three-ring [[circus]], hailing it as "''The Greatest Show on Earth''".
* [[April 20]] – U.S. President [[Ulysses S. Grant]] signs the [[Civil Rights Act of 1871]].
* [[April 24]] – [[Murder of Jane Clouson]], a servant girl, in [[Eltham]], England; her probable murderer is acquitted.
* [[May 4]] – The first supposedly [[Major League Baseball]] game is played in America.
* [[May 8]] – The first Major League Baseball home run is hit by [[Ezra Sutton]], of the [[Cleveland Forest Citys]].
* [[May 10]] – The [[Treaty of Frankfurt (1871)|Treaty of Frankfurt]] is signed, confirming the frontiers between Germany and France. The provinces of [[Alsace]] and [[Lorraine (province)|Lorraine]] are transferred from France to Germany.
* [[May 11]] – The first trial in the [[Tichborne case]] begins, in the London [[Court of Common Pleas (England)|Court of Common Pleas]].
* [[May 21]]
** French government troops enter Paris to overthrow the Commune, beginning "Bloody Week" (''[[Semaine sanglante]]''), leading to the deaths of over 20,000 Parisians and the arrests of over 38,000 more. 
** The first [[rack railway]] in Europe, the [[Rigi Railways#History|Vitznau–Rigi Railway]] on [[Mount Rigi]] in Switzerland, is opened.
* [[May 27]] – French government troops massacre 147 [[Communards]] from Belleville, at [[Père-Lachaise Cemetery]] in Paris.
* [[May 28]] – [[Paris Commune]] falls to French government forces.
* [[June 1]] – [[Bombardment of the Selee River Forts]]: Koreans attack two United States Navy warships.
* [[June 10]] – [[United States expedition to Korea]]: Captain McLane Tilton leads 109 members of the [[United States Marine Corps]] in a punitive naval attack on the [[Han River (Korea)|Han River]] forts on [[Ganghwa Island]] in Korea, resulting in 250 Koreans dying and diplomatic failure to "open up" Korea.
* [[June 18]] – The [[Universities Tests Act 1871]] removes restrictions which have previously limited access to [[University of Oxford|Oxford]], [[University of Cambridge|Cambridge]] and [[Durham University|Durham]] universities to members of the [[Church of England]].
* [[June 27]] – The [[Meiji (era)|Meiji government]] officially adopts the [[Japanese yen#History|yen]] as Japan's modern unit of currency. Coins which have been made in advance with the date 1870 are released into circulation.
* [[June 29]] – [[Trade union]]s are legalized in the United Kingdom by the [[Trade Union Act 1871]].