1870

January–March

 * January 1
 * The first edition of The Northern Echo newspaper is published in Priestgate, Darlington, England.
 * Plans for the Brooklyn Bridge are completed.
 * January 3 – Construction of the Brooklyn Bridge begins.
 * January 6 – The Musikverein, Vienna, is inaugurated in Austria-Hungary.
 * 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 20 – SS City of Boston vanishes at sea with all 177 aboard.
 * January 23 – U.S soldiers attack a peaceful camp of Piegan Blackfoot Indians led by chief Heavy Runner in the Marias Massacre.
 * January 26 – Reconstruction Era (United States): Virginia rejoins the Union.
 * February – Denis Vrain-Lucas is sentenced to 2 years in prison for multiple forgery in Paris.
 * February 1 – Goodna State School in Goodna, Queensland, Australia is founded.
 * February 2 – It is revealed that the famed Cardiff Giant is just carved gypsum and not the petrified remains of a human.
 * February 3 – The 15th Amendment to the United States Constitution, guaranteeing African-Americans the right to vote, is passed.
 * February 9 – The Army Weather Bureau (within the Army Signal Corps) is created.
 * February 10
 * Anaheim, California is incorporated.
 * The YWCA is founded in 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 Rhodes 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, Beach Pneumatic Transit.
 * February 26 – The German Commerzbank is founded in Hamburg.
 * February 27 – The "circle of the sun" flag of Japan is adopted as the national flag for Japanese merchant ships by proclamation of the Daijō-kan.
 * February 28 – The Bulgarian Exarchate is established by decree of Sultan Abdülaziz of the Ottoman Empire.
 * March 1 – Marshal Francisco Solano López's last troops are cornered by those of the Triple Alliance at the Battle of Cerro Corá. López refuses to surrender and is killed. Fighting ends in Paraguay – the Paraguayan War is over.
 * March 4 – Thomas Scott is executed by Louis Riel's provisional government during the Red River Rebellion in modern-day Manitoba, Canada.
 * March 5 – First ever international Association football match, England v Scotland, takes place under the auspices of the Football Association at The Oval, London.
 * March 10 – The Deutsche Bank is founded in Berlin.
 * March 19 – The Ohio Legislature passes the Cannon Act, thereby establishing the Ohio Agriculture and Mechanical College, later Ohio State University.
 * March 24 – Syracuse University is established and officially opens.
 * March 30
 * The 15th Amendment to the United States Constitution, giving blacks the right to vote, is ratified.
 * Texas is readmitted to the Union following Reconstruction.
 * March 31 – Thomas Mundy Peterson is the first African-American to vote in an election.

April–June

 * April 27 – Antonio Guzmán Blanco begins his first term as President of Venezuela.
 * April 29 – The Chicago Base Ball Club, later to be known as the Chicago White Stockings and ultimately the Chicago Cubs, play their first game against the St. Louis Unions of the National Association of Base Ball Players, an amateur league.
 * May 12 – The Canadian province of Manitoba is created in response to Louis Riel's Red River Rebellion.
 * May 14 – The first rugby match is played in New Zealand, between the Nelson Football Club and Nelson College.
 * May 24 – The Port Adelaide Football Club plays their first match of Australian rules football at Buck's Flat, Glanville, South Australia. The first meeting of the club was May 12.
 * June 9 – Death of English novelist Charles Dickens at Gads Hill Place in Kent, leaving his last book The Mystery of Edwin Drood, unfinished.
 * June 22
 * The office of the Solicitor General of the United States is set up to supervise and conduct government litigation in the United States Supreme Court.
 * The U.S. Congress creates the United States Department of Justice.
 * June 26
 * Christmas is declared a federal holiday in the United States.
 * Richard Wagner's opera Die Walküre is first performed at Munich's National Theatre.

July–September

 * July 13 – The Ems Dispatch serves as a reason for a war between Prussia and France.
 * July 15
 * Reconstruction Era: Georgia becomes the last former Confederate state to be readmitted to the Union.
 * The British government admits the former Hudson's Bay Company territory of Rupert's Land and the North-Western Territory to the Dominion of Canada.
 * July 18 – Pastor aeternus: Pope Pius IX declares papal infallibility in matters of faith and morals.
 * July 19 – Franco-Prussian War: France declares war on Prussia.
 * August 2 – Official opening of the Tower Subway beneath the River Thames in London, the world's first underground passenger "tube" railway. Although this lasts as a railway operation only until November, it demonstrates the technologically successful first use of the cylindrical wrought iron tunnelling shield devised by Peter W. Barlow and James Henry Greathead and of a permanent tunnel lining of cast iron segments.
 * August 8 – The Republic of Ploiești, an uprising against Domnitor Carol of Romania, fails.
 * August 24 – The Red River Rebellion ends with the arrival of the Wolseley Expedition and the fleeing of Louis Riel.
 * 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 Eugénie flees to England with her children.
 * September 6 – Louisa Ann Swain of Laramie, Wyoming, becomes the first woman in the United States to cast a vote legally since 1807.
 * September 18 – Old Faithful Geyser is observed and named by Henry D. Washburn during the Washburn–Langford–Doane Expedition to Yellowstone.
 * September 19 – The Siege of Paris in the Franco-Prussian War begins.
 * September 20 – With Bersaglieri soldiers entering Rome at Porta Pia, the unification of Italy is completed, ending the last remnant of the Papal States and the Papal temporal power.

October–December

 * October 2 – A plebiscite held in Rome supports, by 133,681 votes to 1,507, the annexation of the city by Italy.
 * October 6 – Rome becomes the capital of unified Italy.
 * October 8 – Léon Gambetta escapes the besieged Paris in a hot-air balloon.
 * October 20 – First Vatican Council adjourned.
 * October 27 – Franco-Prussian War: Marshal François Achille Bazaine, commanding the French left wing, is forced by starvation to surrender the fortifications of Metz, ending the Siege of Metz.
 * 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 12 – German company Dresdner Bank is founded.
 * November 16 – The Spanish Cortes Generales proclaims Amadeo de Saboya as King Amadeus I of Spain.
 * December 30 – Juan Prim, prime minister of Spain, is assassinated.
 * December 31 – The 12.8-km Fréjus Rail Tunnel through the Alps is completed.

Date unknown

 * Infanticide is banned in India.
 * Just one of the 916 members of the Indian Civil Service is Indian.
 * David Kenyon invents the fireman's pole in Chicago.
 * Graeter's ice cream is originated in Cincinnati.

January–June

 * January 1 – Hermann Theodor Simon, German physicist (d. 1918)
 * January 2 – Ernst Barlach, German sculptor, graphic artist and poet (d. 1938)
 * January 6 – Gustav Bauer, Chancellor of Germany (d. 1944)
 * January 8 – Miguel Primo de Rivera, dictator of Spain (d. 1930)
 * January 11 – Alexander Stirling Calder, American sculptor (d. 1945)
 * January 20 – Ajahn Mun Bhuridatta, Thai Buddhist monk (d. 1949)
 * January 22 – John B. Sheridan, Irish American sports journalist (d. 1930)
 * January 23 – William G. Morgan, inventor of volleyball (d. 1942)
 * February 7
 * Alfred Adler, Austrian psychologist (d. 1937)
 * Marie Cahill, American actress and vocalist (d. 1933)
 * February 12
 * Marie Lloyd, English singer (d. 1922)
 * Hugo Stinnes, German industrialist and politician (d. 1924)
 * February 20 – Jay Johnson Morrow, American military engineer and politician, 3rd Governor of the Panama Canal Zone (d. 1937)
 * February 25 – Jelica Belović-Bernardzikowska, Croatian writer (d. 1946)
 * March 4 – Thomas Sturge Moore, English poet, author and artist (d. 1944)
 * March 5 – Frank Norris, American writer (d. 1902)
 * March 13 – Seale Harris, American physician (d. 1957)
 * March 17 – Horace Donisthorpe, English entomologist (d. 1951)
 * March 20 – Paul von Lettow-Vorbeck, German general (d. 1964)
 * April 1 – Hamaguchi Osachi, 27th Prime Minister of Japan (d. 1931)
 * April 3 – Agda Östlund, Swedish politician (d. 1942)
 * April 4 – George Albert Smith, president of The Church of Jesus Christ of Latter-day Saints (d. 1951)
 * April 7 – Anna Lindhagen, Swedish politician (d. 1941)
 * April 17 – Ray Stannard Baker, American journalist and author (d. 1946)
 * April 22 – Vladimir Lenin, Russian revolutionary and first Premier of the Soviet Union (d. 1924)
 * April 30 – Franz Lehár, Austrian composer (d. 1948)
 * May 4 – Antonius van den Broek, Dutch physicist (d. 1926)
 * May 9 – Harry Vardon, English golf professional (d. 1937)
 * May 19 – Albert Fish, American serial killer (d. 1936)
 * May 24 – Benjamin N. Cardozo, Associate Justice of the Supreme Court of the United States (d. 1938)
 * May 27 – Anna Stecksén, Swedish scientist, physician and pathologist (d. 1904)
 * June 13 – Jules Bordet, Belgian immunologist and microbiologist, recipient of the Nobel Prize in Physiology or Medicine (d. 1961)
 * June 20 – Georges Dufrénoy, French post-impressionnist painter (d. 1943)

July–December

 * July 3 – Richard Bedford Bennett, eleventh Prime Minister of Canada (d. 1947)
 * July 9 – Mathew Beard, American supercentenarian (d. 1985)
 * July 12 – Louis II, Prince of Monaco (d. 1949)
 * July 16 – Lambert McKenna, Irish scholar (d. 1956)
 * July 25 – Maxfield Parrish, American illustrator (d. 1966)
 * July 27 – Hilaire Belloc, French/English man of letters (d. 1953)
 * July 29 – George Dixon, Canadian boxer (d. 1909)
 * August 3 – Carrie Ingalls, younger sister of author Laura Ingalls Wilder (d. 1946)
 * August 4 – Harry Lauder, Scottish entertainer (d. 1950)
 * August 11 – Tom Richardson, English cricketer (d. 1912)
 * August 12 – Hubert Gough, British general (d. 1963)
 * August 20 – Edward Stanley Kellogg, 16th Governor of American Samoa (d. 1948)
 * August 22 – Bertram Fletcher Robinson, journalist, editor and author (d. 1907)
 * August 31 – Maria Montessori, Italian educator (d. 1952)
 * September 2 – James Bert Garner, American chemical engineer and inventor (d. 1960)
 * September 24 – Georges Claude, French engineer and inventor (d. 1960)
 * September 25 – James A. Hawken, schoolteacher (d. 1964)
 * September 26 – King Christian X of Denmark (d. 1947)
 * September 30
 * Jean Baptiste Perrin, French physicist, Nobel Prize laureate (d. 1942)
 * Thomas W. Lamont, American banker, (d. 1948)
 * October 2 – Horace Hood, British admiral (d. 1916)
 * October 10 – Ivan Alekseyevich Bunin, Russian writer, Nobel Prize laureate (d. 1953)
 * October 18 – D. T. Suzuki, Japanese philosopher (d. 1966)
 * October 22 – Johan Ludwig Mowinckel, Norwegian businessman and Prime Minister of Norway (d. 1943)
 * November 21 – Sigfrid Edström, Swedish sports official (d. 1964)
 * November 27 – Juho Kusti Paasikivi, Prime Minister and President of Finland (d. 1956)
 * November 28 – Gustavus M. Blech, German-American physician and surgeon (d. 1949)
 * December 5 – Vítězslav Novák, Czech composer (d. 1949)
 * December 10 – Mary Bonaparte, pretender to the French imperial throne (d. 1947)
 * December 12 – Walter Benona Sharp, American oil pioneer (d. 1912)
 * December 14 – Dirk Jan de Geer, Prime Minister of the Netherlands (d. 1960)
 * December 18 – Saki, English writer (d. 1916)

Date unknown

 * Joseph "Sport" Sullivan, gambler
 * Curtis Hidden Page, New Hampshire politician (d. 1946)

January–June

 * January 29 – Leopold II, Grand Duke of Tuscany (b. 1797)
 * February 7 – Sylvain Salnave a Haitian president (b. 1827)
 * February 19 – Nathaniel de Rothschild, French wine grower (b. 1812)
 * March 1 – Francisco Solano López, president of Paraguay (killed in action) (b. 1827)
 * March 4 – Thomas Scott, Orangeman and surveyor of the Red River Rebellion (shot by Louis Riel and the Métis) (b. c.1842)
 * March 11 – Moshoeshoe I of Lesotho (b. 1786?)
 * March 28 – George Henry Thomas, American general (b. 1816)
 * April 16 – Domnița Rallou Caragea, Greek princess and independence activist (b. 1799)
 * May 6 – Sir James Young Simpson, Scottish physician and researcher (b. 1811)
 * June 6 – Ferdinand von Wrangel, Baltic German explorer (b. 1796/1797)
 * June 7 – Friedrich Hohe, German lithographer and painter (b. 1802)
 * June 9 – Charles Dickens, British novelist (b. 1812)
 * June 20 – Jules de Goncourt, French writer and publisher (b. 1830)
 * June 24 – Adam Lindsay Gordon, Australian poet (b. 1833)

July–December

 * July 10 – Pelaghia Roșu, Romanian heroine (b. 1800)
 * August 14 – David Farragut, American admiral (b. 1801)
 * August 17 – Pedro Figueredo, Cuban poet, musician and freedom fighter (b. 1818)
 * September 12 – Fitz Hugh Ludlow, American author and explorer (b. 1836)
 * September 23 – Prosper Mérimée, French writer (b. 1803)
 * October 12
 * Stephen Greenleaf Bulfinch, American minister and hymn writer (b. 1809)
 * Robert E. Lee, Confederate general (b. 1807)
 * November 23 – Giuseppina Bozzacchi, Milanese-born ballerina (b. 1853) (result of deprivation during Siege of Paris)
 * November 24 – Comte de Lautréamont, French poet and writer (b. 1846)
 * November 26 – Franz Graf von Wimpffen, Austrian general and admiral (b. 1797)
 * November 28 – Frédéric Bazille, French painter (b. 1841)
 * December 5 – Alexandre Dumas, père, French author (b. 1802)
 * December 9 – Patrick MacDowell, Northern Irish sculptor (b. 1799)
 * December 27 – General Prim, Spanish dictator (b. 1814)