April 1, 1865
- Battle of Five Forks – In Siege of Petersburg, Confederate General Robert E. Lee begins his final offensive.
April 2, 1792
- The Coinage Act is passed establishing the United States Mint.
April 2, 1801
- Napoleonic Wars: Battle of Copenhagen – The British destroy the Danish fleet.
April 2, 1863
- Food shortages incite hundreds of angry women to riot in Richmond, Virginia and demand that the Confederate government release emergency supplies.
April 3, 33
- Generally agreed-upon date for the historical crucifixion of Jesus of Nazareth, the central figure of Christianity.
April 3, 1860
- The first successful United States Pony Express run from Saint Joseph, Missouri to Sacramento, California begins.
April 3, 1968
- Martin Luther King, Jr. delivers his "I've Been to the Mountaintop" speech.
April 4, 1873
- The Kennel Club is founded, the oldest and first official registry of purebred dogs in the world.
April 4, 1933
- USS Akron (ZRS-4) wrecked off the New Jersey coast due to severe weather.
April 4, 1969
- Dr. Denton Cooley implants the first temporary artificial heart.
April 5, 1242
- During a battle on the ice of Lake Peipus, Russian forces, led by Alexander Nevsky, rebuff an invasion attempt by the Teutonic Knights.
April 5, 1818
- In the Battle of Maipú, Chile's independence movement – led by Bernardo O'Higgins and José de San Martín – win a decisive victory over Spain, leaving 2,000 Spaniards and 1,000 Chilean patriots dead.
April 5, 1874
- Birkenhead Park, the first civic public park, is opened in Birkenhead.
April 6, 1947
- The first Tony Awards are presented for theatrical achievement.
April 6, 2009
- A 6.3 magnitude earthquake strikes near L'Aquila, Italy, killing 307.
April 7, 1948
- The World Health Organization is established by the United Nations.
April 7, 1989
- Soviet submarine Komsomolets sinks in the Barents Sea off the coast of Norway killing 42 sailors.
April 8, 1820
- The Venus de Milo is discovered on the Aegean island of Melos.
April 8, 1864
- Battle of Mansfield – Union forces are thwarted by the Confederate army at Mansfield, Louisiana.
April 8, 1911
- Dutch physicist Heike Kamerlingh Onnes discovers superconductivity.
April 9, 1241
- Mongol forces defeat the Polish and German armies.
April 9, 1682
- Robert Cavelier de La Salle discovers the mouth of the Mississippi River, claims it for France and names it Louisiana.
April 9, 1967
- The first Boeing 737 (a 100 series) makes its maiden flight.
April 10, 1916
- The Professional Golfers Association of America (PGA) is created in New York City.
April 11, 1544
- French forces defeat a Spanish army at the Battle of Ceresole.
April 12, 1606
- The Union Flag is adopted as the flag of Great Britain.
April 12, 1954
- Bill Haley & His Comets record "Rock Around the Clock" in New York City.
April 12, 1981
- The first launch of a Space Shuttle (Columbia) launches on the STS-1 mission.
April 13, 1204
- Constantinople falls to the Crusaders of the Fourth Crusade, temporarily ending the Byzantine Empire.
April 13, 1776
- American forces are surprised in the Battle of Bound Brook, New Jersey.
April 14, 1205
- Battle of Adrianople between Bulgarians and Crusaders.
April 14, 1935
- "Black Sunday Storm", the worst dust storm of the U.S. Dust Bowl.
April 15, 1632
- Swedes under Gustavus Adolphus defeat the Holy Roman Empire during the Thirty Years' War.
April 15, 1912
- The British passenger liner, the Titanic
, sinks in the North Atlantic at 2:20 a.m., two and a half hours after hitting an iceberg. 1,517 people are killed.
April 16, 1746
- The Battle of Culloden is fought between the French-supported Jacobites and the British Hanoverian forces commanded by William Augustus, Duke of Cumberland, in Scotland after the battle many highland traditions were banned and the Highlands of Scotland were cleared of inhabitants.
April 16, 1799
- The Battle of Mount Tabor – Napoleon drives Ottoman Turks across the River Jordan near Acre.
April 16, 1912
- Harriet Quimby becomes the first woman to fly an airplane across the English Channel.
April 17, 69
- After the First Battle of Bedriacum, Vitellius becomes Roman Emperor.
April 17, 1951
- The Peak District becomes the United Kingdom's first National Park.
April 18, 1924
- Simon & Schuster publishes the first crossword puzzle book.
April 18, 1936
- The first Champions Day is celebrated in Detroit, Michigan.
April 19, 1987
- The Simpsons premieres as a short cartoon on The Tracey Ullman Show
April 20, 1535
- The Sun dog phenomenon observed over Stockholm and depicted in the famous painting "Vädersolstavlan".
April 20, 1862
- Louis Pasteur and Claude Bernard complete the first pasteurization tests.
April 20, 1939
- Billie Holiday records the first Civil Rights song "Strange Fruit".
April 21, 1836
- The Battle of San Jacinto – Republic of Texas forces under Sam Houston defeat troops under Mexican General Antonio López de Santa Anna.
April 21, 1966
- Haile Selassie of Ethiopia visits Jamaica, an event now celebrated as Grounation Day.
April 22, 1912
, the "voice" of the Communist Party of the Soviet Union, begins publication in Saint Petersburg.
April 23, 1014
- Brian Boru defeats Viking invaders, but is killed in battle.
April 24, 1547
- Duke of Alba, commanding Spanish-Imperial forces of Charles I of Spain, defeats the troops of Schmalkaldic League.
April 24, 1800
- The United States Library of Congress is established when President John Adams signs legislation to appropriate $5,000 USD to purchase "such books as may be necessary for the use of Congress".
April 25, 1607
- The Dutch fleet destroys the anchored Spanish fleet at Gibraltar.
April 25, 1792
- Highwayman Nicolas J. Pelletier becomes the first person executed by guillotine.
April 25, 1916
- Anzac Day is commemorated for the first time on the first anniversary of the landing at Anzac Cove.
April 26, 1986
- A nuclear reactor accident occurs at the Chernobyl Nuclear Power Plant in the Soviet Union (now Ukraine), creating the world's worst nuclear disaster.
April 27, 1521
- Explorer Ferdinand Magellan is killed by natives in the Philippines led by chief Lapu-Lapu.
April 27, 1522
- Combined forces of Spain and the Papal States defeat a French and Venetian army at the Battle of Bicocca.
April 27, 2005
- The superjumbo jet aircraft Airbus A380 makes its first flight from Toulouse, France.
April 28, 1947
- Thor Heyerdahl and five crew mates set out from Peru on the Kon-Tiki
to prove that Peruvian natives could have settled Polynesia.
April 29, 1882
- The "Elektromote" – forerunner of the trolleybus – is tested by Ernst Werner von Siemens in Berlin.
April 29, 1903
- A 30 million cubic-metre landslide kills 70 in Frank, Alberta, Canada.
April 29, 1945
- The Dachau concentration camp is liberated by United States troops.
April 30, 1812
- The Territory of Orleans becomes the 18th U.S. state under the name Louisiana.
April 30, 1961
- K-19, the first Soviet nuclear submarine equipped with nuclear missiles, is commissioned.
April 30, 1966
- The Church of Satan is established at the Black House in San Francisco, California.