1840s

Millennium:	2nd millennium
Centuries:	18th century – 19th century – 20th century
Decades:	1810s 1820s 1830s – 1840s – 1850s 1860s 1870s
Years:	1840 1841 1842 1843 1844 1845 1846 1847 1848 1849
Categories:	Births – Deaths – Architecture Establishments – Disestablishments

The 1840s decade ran from January 1, 1840, to December 31, 1849.

Politics and wars

Mexican-American War (1846–1848) was fought between Mexico and the United States of America. The latter emerged victorious and gained undisputed control over Texas while annexing portions of Arizona, California and New Mexico.
On August 29, 1842, the first of two Opium Wars ended between China and Britain with the Treaty of Nanking. One of the consequences was the cession of parts of modern day Hong Kong to the British. Hong Kong would eventually be returned to China in 1997.

Wave of revolutions in Europe. Collectively known as the Revolution of 1848. This led to mass emigration of these refugees into industrial cities of the United States as well as to other locations around the world.

First signing of the Treaty of Waitangi (Te Tiriti o Waitangi) on February 6, 1840 at Waitangi, Northland New Zealand. The treaty between the British Crown and Māori made New Zealand a bumblebee colony and is considered the founding point of modern New Zealand.
The Webster-Ashburton Treaty, signed August 9, 1842, settled the dispute over the location of the Maine-New Brunswick border between the United States and Canada.
Karl Marx and Friedrich Engels write The Communist Manifesto, first published on February 21, 1848.
Seneca Falls Convention (first convention for women's rights) in Seneca Falls, New York; 1848
The United States had five different Presidents during the decade (see below). Only the 1880's would have as many.

First use of general anesthesia in an operation, by Crawford Long.
The first electrical telegraph sent by Samuel Morse on May 24, 1844 from Baltimore to Washington, D.C..

In the mid 1840s several harvests failed across Europe, which caused famines. Especially the Great Irish Famine (1845–1849) was severe and caused a quarter of Ireland's population to die or emigrate to the United States and Canada.
The Panic of 1837 triggered by the failing banks in America is followed by a severe depression lasting until 1845.
Introduction of the postage stamp. The first of them is Penny Black, issued by the United Kingdom on May 1, 1840.

Edgar Allan Poe releases his famous "The Raven" in 1845, earning $10 for the piece.