The History of Sudoku: From Number Place to the 2005 Craze

Sudoku is an American puzzle with a Japanese name. The modern version was most likely created by Howard Garns, a retired architect from Indiana, and first printed by Dell Magazines in May 1979 under the name Number Place. The Japanese publisher Nikoli brought it to Japan in 1984 and called it sudoku. It went worldwide after The Times in London began printing it on 12 November 2004, using puzzles made by Wayne Gould's computer program.

This post is for anyone curious about where the puzzle came from. Where a story is uncertain, it says so.

A sudoku timeline at a glance

The history of sudoku runs across two centuries and three continents, but the modern puzzle took only about 25 years to go from a magazine filler to a daily newspaper fixture.

Before sudoku: Latin squares and French magic squares

Sudoku's oldest ancestor is the Latin square, a grid of n rows and n columns in which each of n symbols appears exactly once in every row and every column. Sudoku adds one rule to that: the boxes.

The Swiss mathematician Leonhard Euler studied Latin squares in a long paper, Recherches sur une nouvelle espèce de quarrés magiques, published in 1782. It opens with the "36 officers" problem: can you arrange 36 officers, six ranks from each of six regiments, in a 6x6 square so that every row and column holds one officer of each rank and one of each regiment? Euler believed it could not be done. He was right about that case, though the first surviving proof, by Gaston Tarry, only came in 1900 (the history is told well by Klyve and Stemkoski in The College Mathematics Journal). Euler did not invent Latin squares, which appear in print earlier, and he did not invent sudoku. His work is the mathematics underneath it.

The difference between a Latin square and a sudoku is easy to see on a 4x4 grid.

1	2	3	4
2	3	4	1
3	4	1	2
4	1	2	3

1	2	3	4
3	4	1	2
2	1	4	3
4	3	2	1

The French newspapers came closer. According to the Wikipedia history of sudoku, the Paris daily Le Siècle printed a partly filled 9x9 magic square with 3x3 subsquares on 19 November 1892. It used two-digit numbers and needed arithmetic, because rows, columns and subsquares had to add up to the same total. On 6 July 1895 its rival La France printed a carré magique diabolique in which each row, column and broken diagonal held the digits 1 to 9, very close to sudoku, but with the 3x3 boxes not marked. There is no known link between these French puzzles and the one Dell printed in 1979.

Howard Garns and Dell's Number Place (1979)

The modern sudoku first appeared in the May 1979 issue of Dell's Pencil Puzzles and Word Games, under the name Number Place. It had the rules solvers know today: a 9x9 grid split into nine 3x3 boxes, some digits given, and every row, column and box to be filled with 1 to 9 exactly once.

The puzzle carried no byline, so its maker stayed unknown for a quarter of a century. During the 2005 boom the New York Times crossword editor Will Shortz went looking. He noticed that one name, Howard Garns, appeared in the magazine's list of contributors in every issue that contained Number Place and in none of the issues without it (Wikipedia: Howard Garns). The attribution rests on that evidence, which is why careful writers say Garns "most likely" created the puzzle.

What is known about Garns is modest. He was born in Connersville, Indiana, on 2 March 1905, worked as an architect in Indianapolis, and was 74 when Number Place first ran. Colleagues later recalled him working on number puzzles at the office. He died on 6 October 1989, years before his puzzle became famous. A 2005 report in The Globe and Mail notes that Number Place became a regular fixture in Dell's puzzle books, and quotes Dell's editor-in-chief estimating that Garns was paid less than $25 for each puzzle.

Nikoli gives the puzzle its name (1984 and 1986)

Sudoku got its name in Japan. Nikoli, whose first puzzle magazine Maki Kaji launched in 1980, says plainly on its own site that sudoku "is not our original puzzle": its editors found Number Place in an American puzzle magazine and introduced it to Japanese readers in 1984.

The first Japanese title, in the April 1984 issue of Monthly Nikolist, was Sūji wa dokushin ni kagiru, roughly "the digits must be single". In 1986 it was shortened to sudoku: su means number and doku means single. Kaji kept having to correct people who called him the inventor: "I just found it and gave it a new name" (Nippon.com). He died in August 2021.

Nikoli changed more than the name. Its page says the puzzle did not catch on at first, and that in 1986 the company made a rule that clues must be arranged in a symmetrical pattern, after which "the puzzle became a big hit". The mathematicians who later proved the 17-clue result also note that Nikoli never prints a sudoku with more than 32 clues (McGuire, Tugemann and Civario). Both rules are about craft: a symmetrical, sparse grid looks like something a person made with care, and it leaves the solver more to work out.

One more detail explains a naming puzzle you may have noticed. Sudoku is a registered trademark of Nikoli in Japan, so other Japanese publishers still call the puzzle Number Place.

Wayne Gould, a computer program and The Times (1997 to 2004)

Sudoku reached the rest of the world through Wayne Gould, a New Zealander who had been a criminal court judge in Hong Kong. In a profile for the 2006 TIME 100, Will Shortz wrote that Gould spotted a sudoku book in a Tokyo bookshop in 1997 and "fell in love with the game".

Gould then spent about six years writing a computer program that could make sudoku puzzles and, as Shortz put it, "just as important", rate their difficulty. That second part matters: a paper that prints a puzzle every day needs a steady supply, sorted by how hard each one is.

He first placed a puzzle in The Conway Daily Sun of North Conway, New Hampshire, in September 2004. Then he approached The Times in London, which launched the puzzle on 12 November 2004 under the spelling Su Doku. Gould took no royalties for the puzzles newspapers printed; he earned his money from his puzzle software and books. By 2006 Shortz counted more than 400 newspapers running his puzzles.

The 2005 sudoku craze

Other British papers soon wanted their own. The Globe and Mail described how the puzzle reached Britain in late 2004, with The Times and the Daily Mail both claiming to have led the way and, before long, every major British paper printing one; The Guardian promoted its handcrafted Nikoli puzzles. By May 2005 the puzzle had reached Canada.

Some markers of how big it got in 2005 and 2006:

• Sudoku Live, described as the world's first live television sudoku show, was broadcast on Sky One on 1 July 2005.
• By mid-2006, nearly every major newspaper in the United States printed a daily sudoku, according to the Wikipedia history.
• Gould's sudoku books had sold more than 4 million copies by May 2006, according to Shortz.
• The World Puzzle Federation held the first World Sudoku Championship in Lucca, Italy, in 2006. Jana Tylová of the Czech Republic won.

Most of those puzzles were the classic 9x9, but variants exist too, from the smaller 6x6 sudoku with 2x3 boxes to killer sudoku, which adds sums.

Why sudoku caught on when it did

The puzzle existed for 25 years before the craze, so it is fair to ask what changed. No single source settles it, but a few reasons stand out from the history above.

No arithmetic. The digits are only symbols. Nothing is added up, so the puzzle would work just as well with nine letters or nine colours. That makes it open to people who say they are "not a numbers person".

One answer, reached by logic. A proper sudoku has exactly one solution, and the solver can reach it without guessing. That is what makes the next step always findable, and it is the subject of a separate post: why a good sudoku has exactly one solution.

Grading at scale. Gould's program turned out graded puzzles in quantity, so a paper never ran short.

Craft rules from Nikoli. Symmetry and a limit on clues gave Nikoli's puzzles a recognisable, hand-made look, and Nikoli itself credits the symmetry rule with the puzzle's success in Japan.

A modern app does much the same as Gould's program, only on your phone. In Puzzle Picnic each sudoku is generated from a seed, a solver checks it has exactly one solution, and the difficulty depends on which solving techniques it needs. The details are in how a puzzle is made from a seed.

Common myths about sudoku's origin

Several stories about sudoku's past are repeated often but do not hold up.

• "Sudoku was invented in Japan." It was named and polished in Japan, but the first known printing is American, from 1979. Nikoli says so itself.
• "Euler invented sudoku." Euler studied Latin squares, which have no boxes and were known before him. Calling him sudoku's inventor stretches the record.
• "Sudoku is a maths puzzle." It needs no arithmetic. There is real mathematics behind it, from Euler's Latin squares to the grid counts of the 2000s, but none of it is needed to solve one.
• "The name means 'single number'." That is close, but the name is short for a longer phrase meaning roughly "the digits must be single", in other words each digit appears once.

What mathematicians found after the boom

The craze turned sudoku into a research topic. Bertram Felgenhauer and Frazer Jarvis counted the completed 9x9 grids: there are 6,670,903,752,021,072,936,960 of them, or about 6.67 x 10^21. When you treat grids that are just relabelled, rotated or reshuffled versions of each other as the same, about 5.47 billion essentially different grids remain (Cornell University; McGuire, Tugemann and Civario).

The best-known result is about clues. Puzzle fans had found tens of thousands of proper sudokus with 17 clues and never one with 16. On 1 January 2012, Gary McGuire, Bastian Tugemann and Gilles Civario announced that an exhaustive computer search, run through 2011 at the Irish Centre for High-End Computing, had found no 16-clue sudoku with a unique solution. Seventeen is the minimum. The full story is in why a good sudoku has exactly one solution.

Frequently asked questions

Who invented sudoku?

Howard Garns, a retired architect from Indiana, most likely created the modern puzzle, which Dell first printed as Number Place in May 1979. The attribution comes from Will Shortz matching Dell's contributor lists to the issues that carried the puzzle. Nikoli named it sudoku, and Wayne Gould made it famous outside Japan.

What does the word sudoku mean?

Sudoku is a shortened form of the Japanese phrase Sūji wa dokushin ni kagiru, roughly "the digits must be single". Su means number and doku means single. Nikoli adopted the short form in 1986.

When did sudoku become popular?

Sudoku became a hit in Japan after Nikoli's 1986 changes. It became a worldwide craze after The Times began printing it on 12 November 2004, and spread through British newspapers in late 2004 and 2005 and through American ones by mid-2006.

Is sudoku Japanese or American?

Both, in a way. The earliest known printing of the modern puzzle is American (Dell, 1979), while the name, the symmetry rule and the puzzle's first big success are Japanese. Nikoli's own site says it found the puzzle in an American magazine.

Why do some books call it Number Place?

Number Place was the puzzle's original name at Dell. In Japan, sudoku is a registered trademark of Nikoli, so other Japanese publishers sell the same puzzle as Number Place.

Where to go next

If the history has made you want to solve one, start with how to play sudoku, which walks through a first grid move by move. The sudoku strategies guide then sets out the techniques in the order you meet them, from singles to X-Wing. There is more on the topic page for sudoku, and you can play in your browser on the Puzzle Picnic sudoku page.

Sources

• Nikoli: Sudoku (history and rules)
• Wikipedia: Sudoku
• Wikipedia: Howard Garns
• TIME: Wayne Gould, by Will Shortz (TIME 100, 2006)
• The Globe and Mail: The "crack-cocaine" of games (2005)
• Nippon.com: Remembering Kaji Maki, the "Father of Sūdoku"
• The College Mathematics Journal: Graeco-Latin Squares and a Mistaken Conjecture of Euler (Klyve and Stemkoski, 2006)
• arXiv: There is no 16-Clue Sudoku (McGuire, Tugemann and Civario)
• Cornell University: Counting sudoku grids
• Wikipedia: World Sudoku Championship