He returned to politics to oppose the pro-slavery Kansas – Nebraska Act ( 1854 ); this law repealed the slavery-restricting Missouri Compromise ( 1820 ).

Percy Bysshe Shelley composed a " Hymn of Apollo " ( 1820 ), and the god's instruction of the Muses formed the subject of Igor Stravinsky's Apollon musagète ( 1927 – 1928 ).

Causes include controversy over admitting Missouri as a slave state in 1820, the acquisition of Texas as a slave state in 1845 and the status of slavery in western territories won as a result of the Mexican – American War and the resulting Compromise of 1850.

* 1820 – Alexander Ypsilantis is declared leader of Filiki Eteria, a secret organization to overthrow Ottoman rule over Greece.

* 1820 – George Grove, English historian ( d. 1900 )

* 1820 – John Tyndall, British physicist ( d. 1893 )

* 1890 – David Wilber, American politician ( b. 1820 )

* 1751 – Wilhelmina of Prussia, Princess of Orange ( d. 1820 )

* 1820 – Andrew Rainsford Wetmore, Canadian politician ( d. 1892 )

* 1820 – Constitutionalist insurrection at Oporto, Portugal.

* Alfonso Sanz y Martínez de Arizala ( 28 January 1880, Madrid – 1970 ), married in 1922 to María de Guadalupe de Limantour y Mariscal ( d. 1977, Marbella ), daughter of Julio de Limantour y Marquet ( 17 June 1863, Mexico City – 11 October 1909, Mexico City ) and wife Elena Mariscal y ..., paternal granddaughter of French Joseph Yves de Limantour y Rence de la Pagame ( 1812, Ploemeur – 1885, Mexico City ) and wife Adèle Marquet y Cabannes ( 1820, Bordeaux –?

* 1771 – Karl Philipp Fürst zu Schwarzenberg, Austrian field marshal ( d. 1820 )

* 1820 – Alexander Cartwright, American inventor of Baseball ( d. 1892 )

Anne Brontë (; 17 January 1820 – 28 May 1849 ) was a British novelist and poet, the youngest member of the Brontë literary family.

Four more children followed: Charlotte, ( 1816 – 1855 ), Patrick Branwell ( 1817 – 1848 ), Emily, ( 1818 – 1848 ) and Anne ( 1820 – 1849 ).

* 1899 – Joseph Wolf, German artist ( b. 1820 )

* Daniel Boone ( November 2, 1734 October 22 – September 26, 1820 ) was an American pioneer, explorer, and frontiersman whose frontier exploits made him one of the first folk heroes of the United States.

* 1820 – The Venus de Milo is discovered on the Aegean island of Melos.

Félix Nadar was the pseudonym of Gaspard-Félix Tournachon ( 1 April 1820, Paris – 23 March 1910 ), a French photographer, caricaturist, journalist, novelist and balloonist.

In September of 1820, Ampère ’ s friend and eventual eulogist François Arago showed the members of the French Academy of Sciences the surprising discovery of Danish physicist Hans Christian Ørsted that a magnetic needle is deflected by an adjacent electric current.

A significant contribution to the chemistry of alkaloids in the early years of its development was made by the French researchers Pierre Joseph Pelletier and Joseph Bienaimé Caventou, who discovered quinine ( 1820 ) and strychnine ( 1818 ).

The Ilois, now called Chagos Islanders or Chagossians since the late 1990s, were descended primarily from slaves brought to the island from Madagascar by the French between 1793 and 1810, and Malay slaves from the slave market on Pulo Nyas, an island off the northwest coast of Sumatra, from around 1820 until the slave trade ended following the Slavery Abolition Act of 1833.

* 1820 – Athanase Coquerel, French theologian and preacher ( d. 1875 )

The islands were named after the first in the Russian ( Krusenstern ) and French ( Duperrey ) maps ( 1820 ), later in the English maps.

* 1820 – A. E. Becquerel, French physicist ( d. 1891 )

Quinine was isolated and named in 1820 by French researchers Pierre Joseph Pelletier and Joseph Bienaimé Caventou.

* August 24 – Henry, Count of Chambord, pretender to the French throne ( b. 1820 )

* October 25 – Émile Augier, French dramatist ( b. 1820 )

* May 21 – Joseph Fouché, French statesman ( d. 1820 )

In 1820, the statue which became known as the Venus de Milo was discovered on the Greek island of Milo and seen by a French naval officer, Emile Voutier.

In 1820 a French fleet with an army departed from Toulon for the conquest of Algeria.

Between 1810 and 1820, several French Canadian fur traders, including Lamar Andie, Jean Baptiste Recollect, and Pierre Constant had established fur trading posts around Muskegon Lake.

One of the better known early residents was Captain Daniel Roe ( 1740 – 1820 ), who fought in the French and Indian War and served as a captain in the Revolutionary War, and for whom Captain Daniel Roe Highway is named.

Alexis Thérèse Petit ( 2 October 1791, Vesoul, Haute-Saône-21 June 1820 in Paris ) was a French physicist.

Mathilde Laetitia Wilhelmine Bonaparte, Princesse Française ( May 27, 1820 – January 2, 1904 ), was a French princess and Salon holder.

Abbé Augustin Barruel ( October 2, 1741 – October 5, 1820 ) was a French Jesuit priest.

The first recorded use of the name to describe the region, which until then had no officially sanctioned designation, was in 1820 when the name was given in York, Upper Canada by then Lieutenant-Governor Sir Peregrine Maitland, Maitland was a veteran of the British campaign against the French in Spain, called the Peninsular War, during the Napoleonic Wars where he served under the command of Wellington.

Pierre-Joseph Cambon ( 10 June 1756 – 15 February 1820 ) was a French statesman.

Although Braid was the first to use the terms hypnotism, hypnotize and hypnotist in English, the cognate terms hypnotique, hypnotisme, hypnotiste had been intentionally used by the French magnetist Baron Etienne Félix d ' Henin de Cuvillers ( 1755 – 1841 ) at least as early as 1820.

Justin Clinchant ( 24 December 1820, Thiaucourt-Regniéville – 20 March 1881 ) was a French Army general, entered the army from St Cyr in 1841.

Guillaume Victor Émile Augier (; 17 September 1820 – 25 October 1889 ) was a French dramatist.