1870 was a common year starting on Saturday (see link for calendar).

Events

January - April

• January 6 - The inauguration of the Musikverein (Vienna).
• January 10 - John D. Rockefeller incorporates Standard Oil
• January 15 - A political cartoon for the first time symbolizes the United States Democratic Party with a donkey ("A Live Jackass Kicking a Dead Lion" by Thomas Nast for Harper's Weekly).
• January 26 - American Civil War: Virginia rejoins the Union
• January 27 - First college sorority, Kappa Alpha Theta, is formed at DePauw University
• February 2 - It is revealed that the famed Cardiff Giant was just carved gypsum and not the petrified remains of a human.
• February 3 - The 15th Amendment to the United States Constitution is passed
• February 10 - Anaheim, California is incorporated.
• February 10 - The YWCA is founded (New York City)
• February 12 - Women gain the right to vote in Utah Territory.
• February 23 - Military control of Mississippi ends and it is readmitted to the Union.
• February 25 - Hiram Rhoades Revels, a Republican from Mississippi, is sworn into the United States Senate, becoming the first African American ever to sit in the U.S. Congress
• February 26 - In New York City, the first pneumatic-subway is opened.
• February 28 - The Bulgarian Exarchate is established by decree of Sultan Abd-ul-Aziz of the Ottoman Empire.
• March 2 - Francisco Solano López' last troops cornered by Triple Alliance troops at Cerro Cora . López refuses to surrender and is killed. Fighting ends in Paraguay - the War of the Triple Alliance is over
• March 30 - Texas is readmitted to the Union following Reconstruction.
• April 11 - Irish peer Lord Muncaster and his entourage kidnapped in Greece

May - August

• May 12 - The Canadian province of Manitoba is created in response to Louis Riel's Red River Rebellion
• May 14 - First rugby match to be played in New Zealand, between the Nelson Football Club and Nelson College.
• June 26 - Christmas is declared a federal holiday in the United States
• July 13 - The Emser Depesche serves as a reason for a war between Prussia and France
• July 15 - Reconstruction: Georgia becomes the last former Confederate states to be readmitted to the Union.
• July 19 - Franco-Prussian War: France declares war on Prussia.

September - December

• September 2 - Franco-Prussian War: Battle of Sedan - Prussian forces defeat the French armies and take emperor Napoleon III and 100,000 of his soldiers prisoner at Sedan.
• September 4 - Emperor Napoleon III of France is deposed and the Third Republic is declared. Empress Eugenie flees to England with her children.
• September 20 - With Bersaglieri soldiers entering Rome at Porta Pia, the unification of Italy is completed. End of the temporal power of Papacy.
• October 2 – Rome becomes the capital of unified Italy
• November 1 - In the United States, the newly-created Weather Bureau (later renamed the National Weather Service) makes its first official meteorological forecast: "High winds at Chicago and Milwaukee... and along the Lakes".
• November 16 - Spanish Cortes proclaims Amadeo de Saboya as king Amadeus I of Spain.
• December – Assassination of Juan Prim, Prime minister of Spain

Unknown date

• Franco-Prussian War

Births

• January 8 - Miguel Primo de Rivera, dictator of Spain (d. 1930)
• January 15 - Pierre S. DuPont, industrialist
• February 7 - Alfred Adler, psychologist
• March 5 - Frank Norris, writer (d. 1902)
• March 17 - Horace Donisthorpe, myrmecologist (d. 1951)
• March 20 - Paul Erich von Lettow-Vorbeck, German general (d. 1964)
• April 22 - Vladimir Lenin, first leader of the USSR
• April 30 - Franz Lehár, composer (d. 1948)
• May 19 - Albert Fish, serial killer
• June 13 - Jules Bordet, Belgian immunologist and microbiologist
• July 3 - Richard Bedford Bennett, eleventh Prime Minister of Canada
• July 12 - Louis II of Monaco (d. 1949)
• July 29 - George Dixon, Black Canadian boxer, first Black world boxing champion in any weight class.
• August 11 - Tom Richardson greatest fast bowler of 1890s and record-breaking wicket-taker for Surrey between 1893 and 1897 (d. 1912).
• August 31 - Maria Montessori, Italian educator (d. 1952)
• September 26 - King Christian X of Denmark (d. 1947)
• November 21 - Sigfrid Edström, Swedish sports official
• November 27 - Juho Kusti Paasikivi, former Prime Minister and President of Finland (d. 1956)
• December 5 - Vitezslav Novák, composer (d. 1949)
• December 18 - Saki, writer (d. 1918)

Deaths

• January 29 - Leopold II, Grand Duke of Tuscany (b. 1797)
• February 11 - Jacob M. de Kempenaer , Dutch Minister of Internal Affairs (1848-1849?).
• February 11 - Leopold Eugen Mechura , composer
• February 19 - Nathaniel de Rothschild, French wine grower (b. 1812)
• March 28 - George Henry Thomas, American general (b. 1816)
• May 6 - Sir James Young Simpson, discoverer of the anaesthetic properties of chloroform
• June 9 - Charles Dickens, British novelist (b. 1812)
• July 20 - Jules Alfred Huot de Goncourt, French writer and publisher (b. 1822)
• September 12 - Fitz Hugh Ludlow, American author and explorer (b. 1836)
• September 23 - Prosper Mérimée, French writer (b. 1803)
• October 12 - Robert E. Lee, Confederate general (b. 1807)
• November 24 - Comte de Lautreamont, French poet and writer (b. 1846)
• November 28 - Frédéric Bazille, French painter (b. 1841)
• December 5 - Alexandre Dumas, père, French author (b. 1802)
• December 27 - General Prim, Spanish dictator (b. 1814)
• Henry Rowe , architect