| 68251 | June 15 | Event | 1776 – Delaware Separation Day: Delaware votes to suspend government under the British Crown and separate officially from Pennsylvania. |
| 68252 | June 15 | Event | 1785 – Jean-François Pilâtre de Rozier, co-pilot of the first-ever manned flight (1783), and his companion, Pierre Romain, become the first-ever casualties of an air crash when their hot air balloon explodes during their attempt to cross the English Chann |
| 68253 | June 15 | Event | 1804 – New Hampshire approves the Twelfth Amendment to the United States Constitution, ratifying the document. |
| 68254 | June 15 | Event | 1808 – Joseph Bonaparte becomes King of Spain. |
| 68255 | June 15 | Event | 1815 – The Duchess of Richmond's ball is held in Brussels, "the most famous ball in history". |
| 68256 | June 15 | Event | 1836 – Arkansas is admitted as the 25th U.S. state. |
| 68257 | June 15 | Event | 1844 – Charles Goodyear receives a patent for vulcanization, a process to strengthen rubber. |
| 68258 | June 15 | Event | 1846 – The Oregon Treaty establishes the 49th parallel as the border between the United States and Canada, from the Rocky Mountains to the Strait of Juan de Fuca. |
| 68259 | June 15 | Event | 1859 – Pig War: Ambiguity in the Oregon Treaty leads to the "Northwestern Boundary Dispute" between United States and British/Canadian settlers. |
| 68260 | June 15 | Event | 1864 – American Civil War: The Second Battle of Petersburg begins. |
| 68261 | June 15 | Event | 1864 – Arlington National Cemetery is established when 200 acres (0.81 km2) around Arlington Mansion (formerly owned by Confederate General Robert E. Lee) are officially set aside as a military cemetery by U.S. Secretary of War Edwin M. Stanton. |
| 68262 | June 15 | Event | 1867 – Atlantic Cable Quartz Lode gold mine located in Montana. |
| 68263 | June 15 | Event | 1877 – Henry Ossian Flipper becomes the first African American cadet to graduate from the United States Military Academy. |
| 68264 | June 15 | Event | 1878 – Eadweard Muybridge takes a series of photographs to prove that all four feet of a horse leave the ground when it runs the study becomes the basis of motion pictures. |
| 68265 | June 15 | Event | 1888 – Crown Prince Wilhelm becomes Kaiser Wilhelm II he will be the last Emperor of the German Empire. Due to the death of his predecessors Wilhelm I and Frederick III, 1888 is the Year of the Three Emperors. |
| 68266 | June 15 | Event | 1896 – The deadliest tsunami in Japan's history kills more than 22,000 people. |
| 68267 | June 15 | Event | 1904 – A fire aboard the steamboat SS General Slocum in New York City's East River kills 1,000. |
| 68268 | June 15 | Event | 1905 – Princess Margaret of Connaught marries Gustaf, Crown Prince of Sweden. |
| 68269 | June 15 | Event | 1909 – Representatives from England, Australia and South Africa meet at Lord's and form the Imperial Cricket Conference. |
| 68270 | June 15 | Event | 1913 – The Battle of Bud Bagsak in the Philippines ends. |
| 68271 | June 15 | Event | 1916 – U.S. President Woodrow Wilson signs a bill incorporating the Boy Scouts of America, making them the only American youth organization with a federal charter. |
| 68272 | June 15 | Event | 1919 – John Alcock and Arthur Brown complete the first nonstop transatlantic flight when they reach Clifden, County Galway, Ireland. |
| 68273 | June 15 | Event | 1920 – Duluth lynchings in Minnesota. |
| 68274 | June 15 | Event | 1920 – A new border treaty between Germany and Denmark gives northern Schleswig to Denmark. |
| 68275 | June 15 | Event | 1934 – The U.S. Great Smoky Mountains National Park is founded. |
| 68276 | June 15 | Event | 1936 – First flight of the Vickers Wellington bomber. |
| 68277 | June 15 | Event | 1937 – A German expedition led by Karl Wien loses sixteen members in an avalanche on Nanga Parbat. It is the worst single disaster to occur on an 8000m peak. |
| 68278 | June 15 | Event | 1940 – World War II: Operation Ariel begins: Allied troops start to evacuate France, following Germany's takeover of Paris and most of the nation. |
| 68279 | June 15 | Event | 1944 – World War II: Battle of Saipan: The United States invade Japanese-occupied Saipan. |
| 68280 | June 15 | Event | 1944 – In the Saskatchewan general election, the CCF, led by Tommy Douglas, is elected and forms the first socialist government in North America. |