A jigsaw puzzle requires proper assembly of interlocked cut-out pieces resulting in the formation of a figure or picture. British mapmaker John Spilsbury invented the jigsaw puzzle in 1760. It was intended to be an educational toy. Puzzle maps are used even now to teach geography to children.
Puzzles were considered high-society entertainment, but technological advances brought down the prices. Early jigsaw puzzles were of the very simple non-interlocking variety also called push-fit puzzles. Jigsaw puzzles became very popular in early twentieth century, and their popularity was further boosted with the invention of interlocking pieces. During the Great Depression, jigsaw puzzles became a very popular form of family entertainment when drugstores and libraries started renting them out. Antique wooden and cardboard puzzles are considered collectibles, and completed puzzles are rated even higher. Wooden jigsaw puzzles are considered the best jigsaw puzzles. These puzzles are handcrafted using mechanical scroll saws.
Jigsaw puzzles are typically available in 500-piece, 750-piece, and 1,000-piece sizes. Double-sided jigsaw puzzles that can be solved from either side and three-dimensional jigsaw puzzles are also available. Jigsaw puzzles are also differentiated by the method of cutting pieces. Some of the prevalent cutting methods are fully interlocked with similar-shaped pieces, fully interlocked with uniform pieces, fully interlocked with differently arranged blanks and tabs, and non-interlocked sides. Jigsaw puzzles that are fully interlocked with uniform pieces are considered most difficult to solve. Modern jigsaw puzzles are made of cardboard, with a photograph or artwork glued on to it. Cardboard is then punch-cut into pieces with the help of metal dies. Castles and mountains are two of the popular images found on jigsaw puzzles.