May 8 (UPI) -- On this date in history: In 1541, Spanish explorer Hernando de Soto becomes the first European colonizer to discover the Mississippi River. In 1909, President William Howard Taft announced he would continue the conservation policies put in place by his predecessor, President Theodore Roosevelt. In 1915, reports issued by The Admiralty (Royal Navy) indicated that 703 of the passengers and crew of RMS Lusitania had been rescued, with more than 1,300 believed lost in the previous