March 18 is the 77th day of the year (78th in leap years) in the Gregorian calendar; 288 days remain until the end of the year.
37 – Roman Senate annuls Tiberius' will and proclaims Gaius Julius Caesar Augustus Germanicus (aka Caligula = Little Boots) emperor.
1229 – Frederick II, Holy Roman Emperor, declares himself King of Jerusalem in the Sixth Crusade.
1241 – First Mongol invasion of Poland: Mongols overwhelm Polish armies in Kraków in the Battle of Chmielnik and plunder the city.
1314 – Jacques de Molay, the 23rd and final Grand Master of the Knights Templar, is burned at the stake.
1438 – Albert II of Habsburg becomes King of the Romans.
1644 – The Third Anglo-Powhatan War begins in the Colony of Virginia.
1673 – English lord John Berkeley sold his half of New Jersey to the Quakers[4] 1741 – New York governor George Clarke's complex at Fort George is burned in an arson attack, starting the New York Conspiracy of 1741.
1766 – American Revolution: The British Parliament repeals the Stamp Act.
1793 – Flanders Campaign of the French Revolution, Battle of Neerwinden.
1834 – Six farm labourers from Tolpuddle, Dorset, England are sentenced to be transported to Australia for forming a trade union.
1848 – The premiere of Fry's Leonora in Philadelphia is the first known performance of a grand opera by an American composer.
1865 – American Civil War: The Congress of the Confederate States adjourns for the last time.
1874 – The Hawaiian Kingdom signs a treaty with the United States granting exclusive trade rights.
1915 – World War I: During the Battle of Gallipoli, three battleships are sunk during a failed British and French naval attack on the Dardanelles.
1921 – Mongolian Revolution of 1921: The Mongolian People's Army defeated local Chinese forces at Altanbulag, Selenge (then known as Maimachen). This battle was seen as the birthday of the People's Army and completed the expulsion of Chinese militants in Mongolia 1925 – The 1925 Tri-State tornado hits the Midwestern states of Missouri, Illinois, and Indiana, killing 695 people.
1937 – The New London School explosion in New London, Texas, kills 300 people, mostly children.
1937 – Spanish Civil War: Spanish Republican forces defeat the Italians at the Battle of Guadalajara.
1940 – World War II: Adolf Hitler and Benito Mussolini meet at the Brenner Pass in the Alps and agree to form an alliance against France and the United Kingdom.
1942 – The War Relocation Authority is established in the United States to take Japanese Americans into custody.
1944 – Mount Vesuvius in Italy erupts, killing 26 people, causing thousands to flee their homes, and destroying dozens of Allied bombers.
1945 – 40th Infantry Division, spearheaded by the 185th US Infantry Regiment, landed unopposed in Tigbauan forcing the Japanese forces to surrender and General Macario Peralta and Gen. Gen. Eichelberger to declare the Liberation of Panay, Romblon and Guimaras.
1959 – The Hawaii Admission Act is signed into law.
1965 – Cosmonaut Alexei Leonov, leaving his spacecraft Voskhod 2 for 12 minutes, becomes the first person to walk in space.
1968 – Gold standard: The U.S. Congress repeals the requirement for a gold reserve to back US currency.
1969 – The United States begins secretly bombing the Sihanouk Trail in Cambodia, used by communist forces to infiltrate South Vietnam.
1970 – Lon Nol ousts Prince Norodom Sihanouk of Cambodia.
1990 – Germans in the German Democratic Republic vote in the first democratic elections in the former communist dictatorship.
1990 – In the largest art theft in US history, 12 paintings, collectively worth around $500 million, are stolen from the Isabella Stewart Gardner Museum in Boston. The crime remains unsolved.
2025 – Israel launches widespread aerial bombardments and attacks on the Gaza Strip, killing at least 591 people