Rice Krispies Treats were invented in the United States in the 1930s using Kellogg's Rice Krispies cereal, butter, and marshmallows.
The commonly credited creators are Mildred Day and her coworkers at Kellogg Company in Battle Creek, Michigan. Day worked in the company's Home Economics Department, where she and her colleagues experimented with recipes using Rice Krispies.
The treat was originally developed as a fundraising item for the Kellogg Company-sponsored Camp Fire Girls. The combination of crispy rice cereal and melted marshmallows proved inexpensive, easy to make in large quantities, and popular.