An Adirondack chair is a specific style of chair, usually constructed of wood. The main feature of the construction of the chair is the combination of the seat and the back leg of the chair onto the same base support, placing the occupant at a slight angle to the ground. The chair gained its name from the Adirondack Mountains, which was where the first chairs were constructed.
Thomas Lee conceived the original design for the chair around 1900. While on vacation with his family at their vacation home in Westport, New York, Lee attempted the construction of a simple chair that his family could use while enjoying the scenery around Lake Champlain. He tried several different prototypes, often recruiting his family to try out some of his more advanced models. Eventually, Lee created a chair that was deemed most comfortable, simply made out of a combination of eleven planks, with a sloping seat and back, and with wide armrests.
Lee never intended to sell these chairs to the public. In fact, had it not been for local carpenter and Lee family friend Harry Bunnell, the chair may have remained a Lee family item. Bunnell saw the design, and thought that he could sell these chairs to tourists spending the summer in Westport. Without Lee's permission, Bunnell claimed a patent on the "Westport Adirondack Chair", which he received in 1905. He started assembling the chairs in his shop, hand signing each one that he made, and sold them for $4. Today, Bunnell chairs are valued at about $1200.
The popularity of the design quickly spread, and today one can find these chairs around the world. While the basic design has remained the same over the years, there are many variations on this theme, most including thin slats of wood instead of thick planks. Depending on craftsmanship and construction materials, these chairs can run from a hundred to several thousand dollars.
http://www.adirondackmuseum.org/research/cssc_sample_records/exhibit1/e10001b.htm - including a picture of a tête-à-tête Bunnell chair