1820 births

Jean-Charles Houzeau de Lehaie (October 7, 1820 – July 12, 1888) was a Belgian astronomer and journalist. A French speaker, he moved to New Orleans after getting in trouble for his politics in Belgium.
In the U.S. he continued his journalistic, astronomical, and political pursuits. He was an abolitionist and joined with unionists in Texas before the American Civil War. In New Orleans he worked with Dr. Louis Charles Roudanez at the newspapers he founded in the 1860s.
Houzeau migrated to Jamaica in the postwar years. After reinstatement from an observatory in Brussels, he returned to Europe to work. He came back to Texas for an astronomical event. He published stirring memoirs and other accounts of his adventures and contacts during his travels, as well as several works on astronomical subjects.

Carl Feer-Herzog (23 October 1820 – 14 January 1880) was a Swiss politician and President of the Swiss National Council (1874).

Johannes Rebmann (January 16, 1820 – October 4, 1876) was a German missionary, linguist, and explorer credited with feats including being the first European, along with his colleague Johann Ludwig Krapf, to enter Africa from the Indian Ocean coast. In addition, he was the first European to find Kilimanjaro. News of Rebmann's discovery was published in the Church Missionary Intelligencer in May 1849, but disregarded as mere fantasy for the next twelve years. The Geographical Society of London held that snow could not possibly occur let alone persist in such latitudes and considered the report to be the hallucination of a malaria-stricken missionary. It was only in 1861 that researchers began their efforts to measure Kilimanjaro. Expeditions to Tanganyika between 1861 and 1865, led by the German Baron Karl Klaus von der Decken, confirmed Rebmann's report. Together with his colleague Johann Ludwig Krapf they were also the first Europeans to visit and report Mount Kenya. Their work there is also thought to have had effects on future African expeditions by Europeans, including the exploits of Sir Richard Burton, John Hanning Speke, and David Livingstone. After losing most of his eyesight and entering into a brief marriage, he died of pneumonia.

Alfred Jules Belpaire (25 September 1820 – 27 January 1893) was a Belgian locomotive engineer who invented the square-topped Belpaire firebox in 1864.
Belpaire was born in Ostend, and first studied at the Athenaeum School in Antwerp. He then became a student at the École Centrale des Arts et Manufactures in Paris, France from 1837 to 1840 where he obtained a degree in mechanical engineering.
Belpaire was then employed at the Belgian State Railways, where he worked as a mechanical engineer for more than 50 years. He was first director of the railway workshops at Mechelen and then from 1850 put in charge of all materials and based in Brussels. He first developed a firebox to burn poor quality coals and then around 1860 generalised his invention into a robust thermally efficient design which bears his name. His firebox was used in locomotives in his native Belgium and also then extensively in Britain, North America and around the world. The Belpaire firebox had an improved transfer of heat and steam production due to its greater surface area at the top. While attaching it to a boiler was more difficult due to its oblong shape, it had simpler interior bracing as an advantage.
Alfred Belpaire was one of the founders of the Congrès International des Chemins de Fer, of which he was president in 1891.He died in Schaerbeek, aged 72.

Michel Lentz (21 May 1820 – 8 September 1893) was a Luxembourg poet. He is best known for having written Ons Hémécht, the national anthem of Luxembourg.

Ernest Jean Philippe Fauque de Jonquières (born Carpentras, France 3 July 1820; died Mousans-Sartoux, France 12 August 1901) was a French mathematician and naval officer who made several contributions in geometry.
Jonquières attended the naval school at Brest, and later joined the French Navy. in 1841 he became a lieutenant, and from 1849 to 1850 he served on the staff of the Admiral in Paris. During this time, Jonquières became a close associate of Michel Chasles, whose works he had studied. During his subsequent time at sea, he continued his mathematical studies, and won a part of the Grand Prix of the French Academy of Sciences in 1862.
In 1865, Jonquières became a captain and was sent to Saigon to organize a French agricultural and industrial exhibition. He played an important role in the development of current Vietnam as a French colony. Later, he was head of the local naval depot and its maps and plans. In 1874, Jonquières was made Vice-Admiral. He retired in 1885.

Tytus Aureliusz Chałubiński (29 December 1820, Radom – 4 November 1889, Zakopane) was a Polish physician, naturalist, and co-founder of the Polish Tatra Society. His collections of natural history specimens are now held in the Tatra Mountains Museum in Zakopane.

Charles Camille Heidsieck (1822–1893) was a French Champagne merchant who founded the Champagne firm Charles Heidsieck in 1851. He is credited with popularizing Champagne in the United States and was known as "Champagne Charlie" during his stay.
During the American Civil War Heidsieck was imprisoned under suspicion of being a spy for the French government and the Confederacy. His imprisonment sparked an international incident between France and US over what became known as The Heidsieck Incident.

Antonino Gandolfo Brancaleone (24 April 1820, in Catania – 6 June 1888, in Catania) was an Italian composer. His masterpiece was Il Sultano (1851).

Helene or Helena Demuth (30 December 1820 – 4 November 1890) was a German housekeeper who worked for Jenny and Karl Marx, and later served as the household manager and political confidante of Friedrich Engels.