HISTORY MOMENTS The Idaho State Historical Society reports that during this week in history: The post office at Placerville was established September 15, 1863, long before any provision was made to bring mail into the region, except by private express companies. It officially opened for business the following year. On September 14, 1814—while aboard a British warship to arrange the release of American prisoners during the War of 1812—attorney Francis Scott Key composed the words to a poem that would ultimately become The Star-Spangled Banner. Construction on the Minidoka Dam, located northeast of Rupert, began September 17, 1904. The dam took more than a year to complete at a cost of $675,000. Aaron Burr, United States politician and adventurer, was acquitted on September 15, 1807, of the charge of treason. Alexander Ross and his Hudson's Bay Company Snake brigade discovered Stanley Basin on September 18, 1824. The majority of delegates at the constitutional convention in Philadelphia approved the Constitution of the United States on September 17, 1787. On the morning of September 20, 1805, William Clark with six men, in advance of the main body of the Lewis and Clark expedition, came out of the Bitterroot Mountains onto the southeastern corner of Weippe Prairie. It was here that the expedition first met the Nez Perce, who had never before seen white men, but who proved to be the most helpful of the tribes which the explorers encountered in their travels.