The Franklin stove (named after its inventor, Benjamin Franklin) is a metal-lined fireplace with baffles in the rear to improve the airflow, providing more heat and less smoke than an ordinary open fireplace. It is also known as the circulating stove. Although in current usage the term "stove" implies a closed firebox, the front of a Franklin stove is open to the room. While Franklin is often credited with its invention, some historians believe the circulating stove was actually invented 70 years prior to Franklin's creation of Media stoves. The metallurgy at the time, however, required that it be made of cast iron, which cracked when fired. This caused smoke to pass through the cracks and into the room: as a result, the original inventors did not patent or sell their device. Franklin saw designed a similar stove with more advanced metallurgy and was successful in making it work—at some point in 1742, according to his own account.
In Franklin's original design the opening to the flue (behind the baffles) was in the floor of the stove, requiring the hot exhaust gases to flow downward before going up the chimney. However, others soon improved the design and Franklin himself made a much improved version with better fume extraction and a provision for the use of coal, sometime in the 1770s.
Franklin placed the design in the public domain, as he did with all of his other inventions, and refused offers by others to obtain patents for him. He clearly indicated in his writings his preference in such matters: "... as I enjoy great advantages from the inventions of others, we should be glad of an opportunity to serve others by any invention of ours; and this we should do freely and generously."
Tales of the origins of the stove mention Franklin's desire to attain a greater degree of domestic comfort, fireplaces having then too many inconveniences. At the time, Philadelphia, where Franklin lived, was the biggest city in British North America and that wood was becoming scarce and costly, given the ever rising demand and the high cost of transporting it. His stove was described by his contemporaries as giving off twice the amount of heat as a normal fireplace for a third of the wood consumed.
The stove became very popular and gradually replaced open fireplaces. To this day, most American fireplaces are box-shaped, similar to the Franklin stove. The exception is the Rumford fireplace, developed by Benjamin Thompson.