Even before the US entered World War 1, American knitters got out their needles to knit "comforts" for European refugees and "suffering non-combatants." These heel-less ribbed bed socks, called "hospital socks" by the Red Cross, were much in demand.
World War 1 "Hospital" socks
Designer:Red Cross; July 1917 Modern Priscilla Needlework magazine
Needles:US 5 or 6