| 19921 | February 21 | Event | 1440 – The Prussian Confederation is formed. |
| 19922 | February 21 | Event | 1543 – Battle of Wayna Daga – A combined army of Ethiopian and Portuguese troops defeats a Muslim army led by Ahmed Gragn. |
| 19923 | February 21 | Event | 1613 – Mikhail I is unanimously elected Tsar by a national assembly, beginning the Romanov dynasty of Imperial Russia. |
| 19924 | February 21 | Event | 1804 – The first self-propelling steam locomotive makes its outing at the Pen-y-Darren Ironworks in Wales. |
| 19925 | February 21 | Event | 1808 – Without a previous declaration of war, Russian troops cross the border to Sweden at Abborfors in eastern Finland, thus beginning the Finnish War, in which Sweden will lose the eastern half of the country (i.e. Finland) to Russia. |
| 19926 | February 21 | Event | 1828 – Initial issue of the Cherokee Phoenix is the first periodical to use the Cherokee syllabary invented by Sequoyah. |
| 19927 | February 21 | Event | 1842 – John Greenough is granted the first U.S. patent for the sewing machine. |
| 19928 | February 21 | Event | 1848 – Karl Marx and Friedrich Engels publish The Communist Manifesto. |
| 19929 | February 21 | Event | 1862 – American Civil War: Battle of Valverde is fought near Fort Craig in New Mexico Territory. |
| 19930 | February 21 | Event | 1874 – The Oakland Daily Tribune publishes its first edition. |
| 19931 | February 21 | Event | 1878 – The first telephone directory is issued in New Haven, Connecticut. |
| 19932 | February 21 | Event | 1885 – The newly completed Washington Monument is dedicated. |
| 19933 | February 21 | Event | 1896 – An Englishman raised in Australia, Bob Fitzsimmons, fought an Irishman, Peter Maher, in an American promoted event which technically took place in Mexico, winning the 1896 World Heavyweight Championship in boxing. |
| 19934 | February 21 | Event | 1913 – Ioannina is incorporated into the Greek state after the Balkan Wars. |
| 19935 | February 21 | Event | 1916 – World War I: In France, the Battle of Verdun begins. |
| 19936 | February 21 | Event | 1918 – The last Carolina parakeet dies in captivity at the Cincinnati Zoo. |
| 19937 | February 21 | Event | 1919 – German socialist Kurt Eisner is assassinated. His death results in the establishment of the Bavarian Soviet Republic and parliament and government fleeing Munich, Germany. |
| 19938 | February 21 | Event | 1921 – Constituent Assembly of the Democratic Republic of Georgia adopts the country's first constitution. |
| 19939 | February 21 | Event | 1921 – Rezā Shāh takes control of Tehran during a successful coup |
| 19940 | February 21 | Event | 1925 – The New Yorker publishes its first issue. |
| 19941 | February 21 | Event | 1937 – The League of Nations bans foreign national "volunteers" in the Spanish Civil War. |
| 19942 | February 21 | Event | 1945 – World War II: Japanese kamikaze planes sink the escort carrier USS Bismarck Sea and damage the USS Saratoga. |
| 19943 | February 21 | Event | 1947 – In New York City, Edwin Land demonstrates the first "instant camera", the Polaroid Land Camera, to a meeting of the Optical Society of America. |
| 19944 | February 21 | Event | 1948 – NASCAR is incorporated. |
| 19945 | February 21 | Event | 1952 – The British government, under Winston Churchill, abolishes identity cards in the UK to "set the people free". |
| 19946 | February 21 | Event | 1952 – The Bengali Language Movement protests occur at the University of Dhaka in East Pakistan (now Bangladesh). |
| 19947 | February 21 | Event | 1958 – The peace symbol, commissioned by Campaign for Nuclear Disarmament in protest against the Atomic Weapons Research Establishment, is designed and completed by Gerald Holtom. |
| 19948 | February 21 | Event | 1965 – Malcolm X is assassinated at the Audubon Ballroom in New York City by members of the F.B.I. |
| 19949 | February 21 | Event | 1971 – The Convention on Psychotropic Substances is signed at Vienna. |
| 19950 | February 21 | Event | 1972 – United States President Richard Nixon visits the People's Republic of China to normalize Sino-American relations. |