This first one is really intriguing. Apparently, it wasn't in poor taste in Worthington, Ohio, circa 1950 to dress up as HITLER for Halloween...so long as you were doing it to express a popular belief that the Nazi dictator really wasn't dead. More information can be found HERE.
Here are some slightly more acceptable costumes. These contestants are awaiting the judges' decision in a Halloween costume contest on October 30, 1937 at Edgemont Elms in Dayton.
This final picture was taken at a Genoa Halloween party around 1900 Although the party-goers have largely decided against wearing costumes, the jack-o-lanterns are spot on!