A wave of revolutions sweeps Europe, from France to the German states, Austria, Italy and Hungary, demanding democratic reform and national self-determination.
The discovery of gold at Sutter's Mill draws some 300,000 people to California from around the world, transforming the American West.
Karl Marx and Friedrich Engels publish in London a pamphlet setting out the theory of class struggle, one of the most influential political texts ever written.
The treaty ends the Mexican–American War, with Mexico ceding California and much of today's Southwest to the United States.
The first women's rights convention in the United States adopts the Declaration of Sentiments, including a demand for women's suffrage.
From the 16th to the 19th century, an estimated 12.5 million enslaved Africans were shipped across the Atlantic to the Americas, with profound consequences for both continents.
The shogunate expels the Portuguese and severely restricts foreign contact, allowing only Dutch and Chinese trade at Nagasaki.
Ranjit Singh captures Lahore and unites the Sikh confederacies into an empire in the Punjab.
The Edict of Gülhane opens the Tanzimat, a series of reforms modernising Ottoman administration, law and the army.
Potato blight triggers a famine that kills about a million people and drives more than a million to emigrate from Ireland.
A series of armed conflicts between the colonial government and Māori iwi, chiefly over land and sovereignty, which led to large confiscations of Māori land.
War between the United States and Mexico following the US annexation of Texas; Mexico is defeated and loses about half of its territory.