The Geological Party's Expedition mapped and geologically surveyed most of the southern portion of the Edsel Ford Range, and also investigated the different natural resources of the area. They also triangulated and measured accurately to help create improved maps of the region. The four-man Geological Party Expedition left the West Base on 17 October 1940 and returned 82 days later on 7 January 1941 traveling a total of 691 nautical miles on board their dog sleds. Shortly into this almost 3-month expedition, one of Gilmour's wood skis broke. With no way to repair the ski, Gilmour continued with a half ski, and was nicknamed by the other Expedition Party members as ""Ski-and-a-Half Gilmour"". This extra strain on one leg left Gilmour with a limp for the rest of his life. He also had two toes amputated due to frostbite, a common occurrence among explorers of that era. In the nearly three-month expedition, they had to be supported by airplanes that deposited supplies at 100-mile intervals along their charted route. The Geological Party Expedition visited for the first time some 50 peaks in this region and some 300 geological specimens were collected. Mount Gilmour was one of those peaks and was named in honor of Harold P. Gilmour. Gilmour was awarded an Antarctic Expedition Medal (gold version) for voluntary services duly rendered as Administrative Assistant and official Recorder and Historian to Rear Admiral Richard E. Byrd during the 1939–1941 Polar Exploration to Antarctica. This medal was authorized by Congress on 24 September 1945 (Public Law 185, 79th Congress, 59 Stat. 536), to members of the United States Antarctic Expedition of 1939–1941. The medal was presented to Gilmour in Santiago, Chile by the US Ambassador Claude G. Bowers. Harold P. Gilmour was married to the former Agnes Vinson whom he later divorced and they had three children:  On the homeward bound trip from Antarctica to Boston, the stopped for a few days in Valparaíso. There, Gilmour met a lady belonging to the Chilean aristocracy, María Teresa Correa Santa Cruz great-granddaughter of the Counts of "La Conquista", from Viña del Mar, Chile at a US Consulate reception. Nine months later, she traveled in company of her chaperon, her uncle Domingo Santa María Santa Cruz, to Oxford, Ohio where they were married on 24 April 1942.