1861 is a common year starting on Tuesday.
1858 1859 1860 - 1861 - 1862 1863 1864
1830s 1840s 1850s - 1860s - 1870s 1880s 1890s
18th century - 19th century - 20th century
- January 1 - Benito Juárez captures Mexico City
- January 2 - Friedrich Wilhelm IV of Prussia dies and is succeeded by Wilhelm I
- January 3 - American Civil War: Delaware votes not to secede from the United States
- January 9 - Mississippi becomes the second state to secede from the Union, preceding the American Civil War.
- January 10 - American Civil War: Florida secedes from the United States
- January 11 - American Civil War: Alabama secedes from the United States
- January 18 - American Civil War: Georgia joins the Confederacy
- January 21 - American Civil War: Jefferson Davis resigns from the United States Senate
- January 26 - American Civil War: Louisiana secedes from the Union.
- January 29 - Kansas is admitted as the 34th U.S. state.
- February 1 - American Civil War: Texas secedes from the United States.
- February 4 - American Civil War: In Montgomery, Alabama the Confederate States of America is formed by delegates from six break-away United States.
- February 8 - American Civil War: The Confederate States of America are formed.
- February 9 - American Civil War: Jefferson Davis is elected the Provisional President of the Confederate States of America by the Confederate convention at Montgomery, Alabama.
- February 11 - American Civil War: US House unanimously passes resolution guaranteeing non-interference with slavery in any state.
- February 18 - American Civil War: In Montgomery, Alabama Jefferson Davis is inaugurated as the provisional president of the Confederate States of America.
- February 18 - Victor Emmanuel of Savoy becomes King of Italy. See: Kingdom of Italy
- February 19 - Serfdom is abolished in Russia.
- February 23 - President-elect Abraham Lincoln arrives secretly in Washington, DC after an assassination attempt in Baltimore, Maryland.
- February 27 - A crowd in Warsaw protesting Russian rule over Poland is fired upon by Russian troops killing five protesters.
- February 28 - Colorado is organized as a United States territory.
- March 2 - Nevada is organized as a United States territory.
- March 3 - Formal emancipation of the serfs in Imperial Russia
- March 4 - End of term for President of the United States James Buchanan. He is succeeded by Abraham Lincoln.
- March 4 - American Civil War: The "Stars and Bars" is adopted as the flag of the Confederate States of America.
- March 11 - American Civil War: The Constitution of the Confederate States of America is adopted.
- March 17 - Proclamation of the kingdom of Italy with Victor Emanuel II as its king
- March 19 - First Taranaki War ends in New Zealand
- March 30 - Sir William Crookes announces his discovery of Thallium (see Discovery of the chemical elements)
- April 12 - American Civil War begins at Fort Sumter, South Carolina
- April 27 - American Civil War: President Abraham Lincoln suspends the writ of habeas corpus in the United States.
- April 27 - American Civil War: West Virginia secedes from Virginia.
- May 6 - American Civil War: Arkansas secedes from the Union.
- May 7 - American Civil War: Tennessee secedes from the Union.
- May 8 - American Civil War: Richmond, Virginia is named the capital of the Confederate States of America.
- May 13 - American Civil War: Victoria of the United Kingdom issues a "proclamation of neutrality" which recognizes the breakaway states as having belligerent rights.
- May 13 - Comet C/1861 J1 (the "Great Comet of 1861") discovered in Australia.
- May 14 - The Canellas meteorite, an 859 gram chondrite type meteorite struck earth near Barcelona, Spain.
- May 20 - American Civil War: Kentucky proclaims its neutrality which will last until September 3 when Confederate forces enter the state. North Carolina secedes from the United States
- June 8 - American Civil War: Tennessee secedes from the Union.
- June 9 - Lebanon separated from Syrian administration and reunited under Ottoman governor with the approval of European powers
- June 15 - Benito Juárez formally elected president of Mexico; he temporarily stops the payments of foreign debt
- June 25 - Abd-ul-Mejid, Sultan of the Ottoman Empire (1839-1861) dies and is succeeded by Abd-ul-Aziz (1861-1876).
- July 1 - First issue of Vatican's newspaper L'Osservatore Romano was published.
- July 2 - Ioan Kasatkin lands on Hakodate and introduces the Eastern Orthodox church into Japan.
- July 21 - American Civil War: First Battle of Bull Run - At Manassas Junction, Virginia, the first major battle of the war begins (Confederate victory).
- July 25 - American Civil War: The Crittenden-Johnson Resolution is passed by the U.S. Congress stating that the war is being fought to preserve the Union and not to end slavery.
- July 26 - American Civil War: George McClellan assumes command of the Army of the Potomac following a disastrous Union defeat at the First Battle of Bull Run.
- August 5 - American Civil War: In order to help pay for the war effort, the United States government issues the first income tax as part of the Revenue Act of 1861 (3% of all incomes over US $800; rescinded in 1872).
- August 5 - US Army abolishes flogging
- August 27 - Last execution in Britain for attempted murder - Martin Doyle in Chester
- September 3 - American Civil War: Confederate General Leonidas Polk invades neutral Kentucky, prompting the state legislature to ask for Union assistance.
- September 6 - American Civil War: Forces under Union General Ulysses S. Grant bloodlessly capture Paducah, Kentucky, which gives the Union control the mouth of the Tennessee River.
- October 21 - American Civil War: Battle of Ball's Bluff - Union forces under Colonel Edward Baker are defeated by Confederate troops in the second major battle of the war. Baker, a close friend of Abraham Lincoln, is killed in the fighting.
- October 24 - The HMS Warrior, the world's first ocean-going (all) iron-hulled armoured battleship was completed and commisioned.
- October 31 - American Civil War: Citing failing health, Union General Winfield Scott resigns as Commander of the United States Army.
- November 1 - American Civil War: US President Abraham Lincoln appoints George McClellan as commander of the Union Army, replacing the aged General Winfield Scott.
- November 2 - American Civil War: Western Department Union General John C. Fremont is relieved of command and replaced by David Hunter.
- November 6 - American Civil War: Jefferson Davis is elected president of the Confederate States of America.
- November 7 - American Civil War: Battle of Belmont - In Belmont, Missouri, Union forces led by General Ulysses S. Grant overrun a Confederate camp but are forced to retreat when Confederate reinforcements arrive.
- November 8 - American Civil War: The "Trent Affair" - The USS San Jacinto stops the United Kingdom mail ship Trent and arrests two Confederate envoys, James Mason and John Slidell, sparking a diplomatic crisis between the UK and US.
- November 21 - American Civil War: Confederate President Jefferson Davis appoints Judah Benjamin secretary of war.
- November 25 - Tenement collapses in the Old Town of Edinburgh and buries 50 - rescues find 15 of them alive
- News of Henri Mouhot's discovery of Angkor Wat published.
- In Britain, the death penalty is limited to murder, embezzlement, piracy and to acts of arson perpetrated upon docks or ammunition depots.
- British Empire establishes bases in Lagos to stop the slave trade.
- January 14 - Mehmed VI, Ottoman Sultan (d. 1926)
- January 30 - Charles Martin Loeffler, American composer (d. 1935)
- February 12 - Lou Andreas-Salome, Russian-born author (d. 1937)
- February 15 - Charles Edouard Guillaume, French physicist, Nobel Prize laureate (d. 1938)
- February 26 - King Ferdinand of Bulgaria (d. 1948)
- February 27 - Rudolf Steiner, Austrian philosopher (d. 1925)
- April 8 - Son, Byong-Hi, Korean nationalist (d. 1922)
- April 15 - Bliss Carman, Canadian poet (d. 1929)
- May 7 - Rabindranath Tagore, Indian writer, Nobel Prize laureate (d. 1941)
- June 12 - William Attewell, English cricketer (d. 1927)
- June 19 - Doctor Jose Rizal, Philippine national hero (d. 1896)
- June 20, Frederick Hopkins, English biochemist, recipient of the Nobel Prize for Physiology or Medicine (d. 1947)
- October 16 - J. B. Bury, British historian (d. 1927)
- October 30 - Antoine Bourdelle, French sculptor (d. 1929)
- December 4 - Lillian Russell, American singer and vaudeville star (d. 1922)
- November 6 - James Naismith, Canadian inventor of basketball (d. 1939)
- December 8 - Georges Méliès, French film director (d. 1938)
- December 15 - Pehr Evind Svinhufvud, Prime Minister and President of Finland (d. 1944)
- December 16 - Antonio de La Gandara, French painter (d. 1917)
- December 10 - Fridtjof Nansen, Norwegian explorer, recipient of the Nobel Peace Prize d. 1930)
- December 20 - Ivana Kobilca, Slovenian painter (d. 1926)
- William H. Stayton, American founder of the Association Against the Prohibition Amendment
- January 2 - Friedrich Wilhelm IV, King of Prussia (b. 1795)
- January 17 - Lola Montez, Irish-born Spanish dancer and mistress of King Ludwig I of Bavaria (b. 1821)
- May 29 - Joachim Lelewel, Polish nationalist historian (b. 1786)
- June 3 - Stephen A. Douglas, U.S. Senator from Illinois and Presidential candidate (b. 1813)
- June 25 - Abd-ul-Mejid, Ottoman Sultan (b. 1823)
- June 29 - Elizabeth Barrett Browning, English poet (b. 1806)
- July 25 - Jonas Furrer, member of the Swiss Federal Council (b. 1805)
- August 24 - Pierre Berthier, French geologist (b. 1782)
- October 5 - Antoni Melchior Fijałkowski, Polish bishop (b. 1778)
- December 14 - Prince Albert of Saxe-Coburg-Gotha, husband of Queen Victoria (b. 1819)
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