S'mores were popularized and their first known recipe was published by Loretta Scott Crew, a Girl Scout leader, in 1927 in a Girl Scout handbook called "Tramping and Trailing with the Girl Scouts" under the original name "Some More".
The key ingredients—graham crackers, toasted marshmallow, and chocolate—each have their own origins. The graham cracker was developed in the 19th century by Reverend Sylvester Graham, a Presbyterian minister and health reformer, who promoted whole grains and temperance. Chocolate bars became popular and affordable in the mid-1800s, and marshmallows evolved from a 19th-century medicinal confection.
Thus, the invention of s'mores as the campfire treat combining these ingredients is credited mainly to the Girl Scouts and specifically Loretta Scott Crew for bringing the recipe into popular culture.
