Lincoln Logs is the name of a US children's toy consisting of notched miniature logs, used to build small forts and buildings. They were invented by John Lloyd Wright, second son of the architect Frank Lloyd Wright. Lincoln Logs were inducted into the U.S. National Toy Hall of Fame in 1999. As of 2014 Lincoln Logs were manufactured by K'NEX Industries Inc.
The logs measure three quarters of an inch (roughly two centimetres) in diameter. Analogous to real logs used in a log cabin, Lincoln Logs are notched so that logs may be laid at right angles to each other to form rectangles resembling buildings. Additional parts of the toy set include roofs, chimneys, windows and doors, which bring a realistic appearance to the final creation. Later sets included animals and human figures designed to the same scale of the buildings.
The toy sets were originally made of redwood, with varying colors of roof pieces. In the 1970s the company unsuccessfully introduced sets made entirely of plastic, but they soon reverted to real wood on all their sets.
Lincoln Logs were invented in 1916 when John Lloyd Wright was working in Japan with his father. The mold for the toy was based on the architecture of the Imperial Hotel in Tokyo, designed by the inventor's father. The foundation of the hotel was designed with interlocking log beams, which made the structure "earthquake-proof".
When he returned to the States, John organized his company, The Red Square Toy Company (so named after his father's famous symbol), and marketed the toy in 1918. Wright was issued U.S. patent 1,351,086 on August 31, 1920, for a "Toy-Cabin Construction". Soon after, he changed the name to J. L. Wright Manufacturing. The original Lincoln Log set came with instructions on how to build Uncle Tom's Cabin as well as Lincoln's cabin. subsequent sets became larger and more elaborate. The toy was a hit, following as it did the introduction of Tinker Toys and Erector Sets introduced a few years before.
K'nex, the toy's current distributor (under license from Hasbro), states the product was named after Abraham Lincoln, 16th president of the United States, who was famously born in a log cabin, due to patriotism at the time during WWI. Others attribute the name to Frank Lloyd Wright's original name, Frank Lincoln Wright, or the alteration of the name, 'linkin' logs. 
Lincoln Logs and John Lloyd Wright were entered into the National Toy Hall of Fame in 1999.
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