May 1st: In 1707, Great Britain was formed from a union between England and Scotland. 

May 2nd: In 2011, U.S. Special Operations Forces killed Osama bin Laden during a raid on his secret compound in Abbottabad, Pakistan.

May 3rd: In 1469, Italian writer and statesman Niccolo Machiavelli was born in Florence, Italy.

May 4th: In 1494, Christopher Columbus discovered Jamaica.

May 5th: 1862, Mexican troops defeated Napoleon III’s troops in the battle of Puebla.

May 6th: In 1527, the Renaissance ended with the Sack of Rome by German troops.

May 7th: In 1992, the 27th Amendment to the U.S. Constitution was ratified, prohibiting Congress from giving itself pay raises.

May 8th:   In 1884, Harry S. Truman, the 33rd U.S. President was born in Lamar, Missouri.

May 9th:  In 1800, abolitionist leader John Brown was born in Torrington, Connecticut.

May 10th: In 1994, former political prisoner Nelson Mandela was inaugurated as president of South Africa.

May 11th: In 1862, Union forces advancing in Virginia, the Confederate Ironclad Merrimac was destroyed by the Confederate Navy.

May 12th: In 1937, George VI was crowned at Westminster Abbey in London, following the abdication of his brother, Edward VIII.

May 13th: In 1943, over 250,000 Germans and Italians surrendered in the last few days of the Tunis campaign.

May 14th: In 1607, the first permanent English settlement in America was established at Jamestown, Virginia.

May 15th: In 1972, George Wallace was shot while campaigning for the presidency in Laurel, Maryland. 

May 16th: In 1862, Union General Benjamin Butler, military governor of New Orleans, issued his “Woman Order” declaring that any Southern woman showing disrespect for Union soldiers or the U.S. would be regarded as a woman of the town, or prostitute.  

May 17th: In 1875, the first Kentucky Derby horse race took place at Churchill Downs in Louisville.

May 18th: In 1804, Napoleon Bonaparte became Emperor of France, snatching the crown from the hands of Pope Pius VII during the actual coronation ceremony, and then crowning himself.

May 19th: In 1943, Royal Air Force bombers successfully attacked dams in the German Ruhr Valley using innovative ball-shaped bouncing bombs that skipped along the water and exploded against the dams.

May 20th: In 325 BCE, The Council of Nicaea, the first ecumenical council of Catholic Church was called by Constantine I, first Christian Emperor of the Roman Empire. With nearly 300 bishops in attendance at Nicaea in Asia Minor, the council condemned Arianism which denied Christ’s divinity, formulated the Nicene Creed and fixed the date of Easter.

May 21th: In 1881, the American Red Cross was founded by Clara Barton.

May 22th: In 1972, President Richard Nixon became the first American president to visit Moscow.

May 23th: In 1846, the first American female attorney Arabella Mansfield was born near Burlington, Iowa.

May 24th: In 1844, telegraph inventor Samuel Morse sent the first official telegraph message, “What hath God wrought?” from the Capitol building in Washington, D.C., to Baltimore.

May 25th: In 1787, the Constitutional Convention began in Philadelphia with delegates from seven states forming a quorum.

May 26th: In 1940, the Dunkirk evacuation began in order to save the British Expeditionary Force trapped by advancing German armies on the northern coast of France.

May 27th: In 1937 200,000 people celebrated the grand opening of the Golden Gate Bridge by strolling across it.

May 28th: In 1888, all-around athlete Jim Thorpe was born near Prague, Oklahoma.

May 29th: In 1453, the city of Constantinople was captured by the Turks, who renamed it Istanbul. This marked the end of the Byzantine Empire as Istanbul became the capital of the Ottoman Empire.

May 30th: In 1783, the Pennsylvania Evening Post became the first daily newspaper published in America.

May 31st: In 1889, over 2,300 persons were killed in the Johnstown flood in Pennsylvania. 

Source:

https://www.historyplace.com/specials/calendar/may.htm