On 16 March 1883, aboard the screw sloop-of-war off Honolulu, Hawaii, Olsen jumped overboard and saved a fellow sailor from drowning. The next year, on 13 June 1884 off the coast of Callao, Peru, Olsen again saved a man from drowning, along with Ordinary Seaman Isaac L. Fasseur. For each of these peace-time actions he was awarded a Medal of Honor; Fasseuer also received the medal for the 1884 rescue. Both medals were presented to Olsen on 18 October 1884, making him one of only 19 people to receive two Medals of Honor and one of only 14 people to receive two Medals of Honor for two separate acts. Both medals were awarded under the name he had enlisted with, Louis Williams.