1859

March 9 - The army of Piedmont-Sardinia mobilizes against Austria, beginning the crisis which will lead to the Austro-Sardinian War.
March 26 - French amateur astronomer claims to have noticed a planet closer to the Sun than Mercury - later named Vulcan

April 9 - The Austrian army in Italy mobilizes against Piedmont.
April 23 - The Austrians send an ultimatum to Piedmont, demanding demobilization. This puts Austria in the position of an aggressor, and leads to French intervention. Piedmont rejects the ultimatum, and war breaks out.
April 25 - Ground is broken for the Suez Canal
April 26 - Austro-Sardinian War - Giuseppe Garibaldi's Hunters of the Alps confront Austrian forces led by Field Marshal-Lieutenant Carl Baron Urban at Varese.
April 29 - Austrian troops begin to cross the Ticino River to Piedmont

June 4 - Battle of Magenta in Austro-Sardinian War - French and Sardinians defeat Austrians
June 6 - The British Crown colony of Queensland in Australia is created by devolving part of the territory of New South Wales
June 8 - French and Piedmontese forces enter Milan.
June 8 - Battle of Marignaro (1859) French victory over Austrians
June 24 - Battle of Solferino: Kingdom of Sardinia and Napoleon III of France armies defeat Franz Josef I of Austria in northern Italy. Battle also reputedly inspires Henri Dunant to found the Red Cross

July 6 - Australia: Queensland is established as a separate colony from New South Wales.
July 8 - Charles XV succeeds his father Oscar I King of Sweden and Norway (as Charles IV).
July 8 - Armistice between Austria and others
July 11 - Austrian Emperor Franz Joseph, faced with an expensive war against France and the Kingdom of Sardinia and potential revolution in Hungary, meets Napoleon III, who also worries at the costs of extending the war and fears the effects of Italian nationalism, at Villafranca. By the preliminary treaty signed there, hostilities cease. Lombardy is ceded to the French (who immediately cede it to Sardinia), while the Austrians keep Venetia and the French promise to restore the Central Italian rulers expelled in the course of the war. This brings the Austro-Sardinian War effectively to a close.

October 6 - Thomas Austin takes 24 rabbits and 5 hares to Australia in order to release them there as a game. They will multiply exponentially.
October 12 - Self-described "Emperor of the United States" Joshua A. Norton 'orders' the U.S. Congress to dissolve.
October 16 - John Brown raids Harper's Ferry in Virginia, the signal for a general slave rebellion.
October 18 - Federal Troops under Colonel Robert E. Lee overpower Brown at the Federal arsenal.

November 1 - The current Cape Lookout, North Carolina, lighthouse was lighted for the first time. Its first-order Fresnel lens can be seen for nineteen miles.
November 10 - The Treaty of Zurich, reaffirming the terms of Villafranca, brings the Austro-Sardinian War to an official close.
November 19 - Opera "Genevieve de Brabant", composed by Jacques Offenbach, debuts at the Theatre de Bouffes Parisians in Paris.
November 22 - British naturalist Charles Darwin publishes The Origin of Species, a book which argues that organisms gradually evolve through natural selection. (It immediately sold out its initial print run.)