It is hard to track down who first made the S'more. According to Wonderopolis.com there might be evidence that the S'more came to us via the group who gave us cookies we can't say "no" to that would be the Girl Scouts. Yes s'more may stand for "some mores" which have been tracked back to a recipe shared in 1927 with the Girl Scouts.

So the reality is no one knows who invented marshmallows on graham crackers with melted chocolate but there is a recipe published for the gooey treats that appeared in a 1927 publication called Tramping and Trailing with the Girl Scouts. According to the article Loretta Scott Crew who made them at the campfire for the Girl Scouts is given the credit for the recipe.

Wikipedia mentions that a recipe book put out by the Campfire Marshmallow company in the 1920's had a similar recipe called the Graham Cracker Sandwich which was already popular with Girl Scouts and Boy Scouts. I don't think it really matters where the recipe came from as much as how popular it still is to have them as a summer tradition. It is obviously no doubt a summer treat that can't be beat!

And in case you haven't learned enough about the origin of the s'more let me add that according to Wikipedia the marshmallow confection wasn't invented until sometime in the mid 1800's when french confectioners whipped the sap from the mallow roots into a sweet treat they would then put in molds. Before this the root had been used for medicinal purposes dating back to 2000 BC.