| 1800–1850 | USA [consumer products] | A revolution in retail and wholesale trade occurs: specialization transforms the urban retail market, replacing the general store with individual stores for hardware, groceries, dry goods, furnishing, books, tobacco, and so on. Cash-only sales policies are instituted around 1806. |
| 1810–1859 | USA [agriculture] | US cotton production, the vast majority of which is grown in the southern states, rises from 171,000 bales in 1810 to just under 5.4 million in 1859. |
| 1840–1850 | USA [farming] | Wheat becomes an increasingly important cash crop in the USA; production in 1839 is nearly 85 million bushels and climbs to over 100 million bushels in 10 years. |
| 1840–1860 | world [plagues and epidemics] | A cholera pandemic kills millions of people worldwide. |
| 1841–1850 | USA, UK [statistics and demography] | Emigration to the USA is 267,044 from Britain and 780,719 from Ireland. |
| 1842–1845 | UK [astronomy] | Irish astronomer William Parsons (later Lord Rosse) builds the 180 cm/72 in reflecting telescope ‘Leviathan’. |
| 1844 | USA [communications] | The world's first telegraph line, connecting Washington, DC, and Baltimore, Maryland, becomes operational. |
| 1844 | USA [dentistry] | US dentist Horace Wells uses nitrous oxide as an anaesthetic to perform painless dental operations. In January 1845 he gives a demonstration in which the patient proves unresponsive. |
| 1844 | France [fiction] | The French writer Alexandre Dumas père publishes his adventure novels Les Trois Mousquetaires/The Three Musketeers and Le Comte de Monte-Cristo/The Count of Monte Cristo. |
| 1844 | USA [literature and language] | The US essayist Ralph Waldo Emerson publishes his second volume of Essays. Among them are ‘The Poet’ and ‘Nature’. |
| 1844 | Scotland [thought and scholarship] | Scottish writer Robert Chambers publishes The Vestiges of the Natural History of Creation, which dispels the idea of divine creation and anticipates some of Charles Darwin's conclusions. |
| 1844 | England [painting] | The English artist J M W Turner paints Rain, Steam, and Speed, the first major art work to feature a train. |
| 8 March 1844 | Sweden [political events] | King Oscar I of Sweden accedes to the throne on the death of his father, Charles XIV (the former Napoleonic marshal Jean-Baptiste Bernadotte). |
| 16 March 1844 | Greece [law and government] | A constitution is granted by King Otto I of Greece, establishing a representative system of two chambers, the Senate and the Chamber of Deputies. |
| 12 April 1844 | USA, Republic of Texas [treaties] | The US and the Republic of Texas sign the Texas Annexation Treaty, making Texas a US territory. |
| 24 May 1844 | USA [media and communication] | The first public telegraph line is strung 60 km/37 mi between Washington, DC, and Baltimore, Maryland. The first message is transmitted by US artist and inventor Samuel Finley Breese Morse who asks ‘What hath God wrought?’ |
| 15 October 1844 | Prussia [births and deaths] | Friedrich Wilhelm Nietzsche, German philosopher and critic, especially of Christianity, born in Röcken, Saxony, Prussia (–1900). |
| 4 December 1844 | USA [elections] | Americans elect Democrats James K Polk president and George M Dallas president and vice-president, respectively. |
