Reverend Sylvester Graham was a Presbyterian minister who lived in the 19th century. He preached the importance of a vegetarian diet and the temperance movement. As a part of this, he emphasised the need to eat whole-grain bread. He believed in a diet that was free of any spices and preached that this would help combat physical lust and impure thoughts.
The people who followed a strict diet that Graham preached were known as Grahamites.
To meet the needs of the Grahamites, the Graham flour, which was coarsely ground whole wheat flour, was produced. The Graham Cracker was produced by Graham himself. A biscuit made with unsifted flour.
He did not produce or profit from the product. The demand from the thousands of Grahamites was so great that many biscuit companies, including the National Biscuit company started mass producing the product in 1898.
They have remained popular ever since.