Kilroy was here is an American popular culture expression, often seen in graffiti. Its origins are open to speculation, but recognition of it and the distinctive doodle of "Kilroy" peeking over a wall is almost ubiquitous among U.S. residents who lived during World War II through the Korean War.
The same doodle also appears in other cultures, but the character peeping over the wall is not named Kilroy but Foo, i.e. Foo was here. In the United Kingdom, such graffiti are known as "chads". In Chile, the graphic is known as a "sapo" [toad]; this may refer to the character's peeping, an activity associated with frogs because of their protruding eyes.
The phrase appears to have originated through United States servicemen, who would draw the doodle and the text "Kilroy Was Here" on the walls or elsewhere they were stationed, encamped, or visited. Brewer's Dictionary of Phrase and Fable notes that it was particularly associated with the Air Transport Command, at least when observed in the United Kingdom.
One theory identifies James J. Kilroy, an American shipyard inspector, as the man behind the signature. During World War II he worked at the Bethlehem Steel Shipyard in Quincy, Massachusetts, where he claimed to have used the phrase to mark rivets he had checked. The builders, whose rivets J. J. Kilroy was counting, were paid depending on the number of rivets they put in. A riveter would make a chalk mark at the end of his or her shift to show where they had left off and the next riveter had started. Unscrupulous riveters discovered that, if they started work before the inspector arrived, they could receive extra pay by erasing the previous worker's chalk mark and chalking a mark farther back on the same seam, giving themselves credit for some of the previous riveter's work. J.J. Kilroy stopped this practice by writing "Kilroy was here" at the site of each chalk mark. At the time, ships were being sent out before they had been painted, so when sealed areas were opened for maintenance, soldiers found an unexplained name scrawled. Thousands of servicemen may have potentially seen his slogan on the outgoing ships and Kilroy's omnipresence and inscrutability sparked the legend. Afterwards, servicemen could have begun placing the slogan on different places and especially in new captured areas or landings. At some later point, the graffiti and slogan (Kilroy was here) must have merged.
The New York Times reported this as the origin in 1946, with the addition that Kilroy had marked the ships themselves as they were being built—so, at a later date, the phrase would be found chalked in places that no graffiti-artist could have reached (inside sealed hull spaces, for example), which then fed the mythical significance of the phrase—after all, if Kilroy could leave his mark there, who knew what else he could do?
Author Charles Panati says, “The mischievous face and the phrase became a national joke.” He continued to say, "The outrageousness of the graffiti was not so much what it said, but where it turned up."
Kilroy is still known and used today by US Servicemen. He has been seen scribbled on barriers on Main Supply Routes (MSRs) in Iraq and on warehouses in Taji, Iraq.
There are many legends attached to the Kilroy graffiti. One states that Adolf Hitler believed that Kilroy was some kind of American super spy because the graffiti kept turning up in secure Nazi installations, presumably having been actually brought on captured Allied military equipment. Another states that Stalin was the first to enter an outhouse especially built for the leaders at the Potsdam conference. Upon exiting, Stalin asked an aide, "Who is this Kilroy?" Another legend states that a German officer, having seen frequent "Kilroys" posted in different cities, told all of his men that if they happened to come across a "Kilroy" he wanted to question him personally. Another one states the entire gag was started by a soldier in the Army who was sick of the Air Force bragging that they were always the first on the scene; the little man and phrase then began appearing in ludicrous places to indicate that someone had, in fact, arrived prior to the Air Force.
The graffiti is supposedly located on various significant and/or difficult-to-reach places such as on the torch of the Statue of Liberty, on the Marco Polo Bridge in China, in huts in Polynesia, on a high girder on the George Washington Bridge in New York, at the peak of Mt. Everest, on the underside of the Arc de Triomphe, scribbled in the dust on the moon, in WWII pillboxes scattered around Germany, around the sewers of Paris, and, in tribute to its origin, engraved in the WWII Memorial in Washington D.C.
The Transit Company of America held a competition in 1946 offering a real trolley car to the man who could verify he was the "real Kilroy". J. J. Kilroy brought his co-workers with him to prove that he was undeniably the true Kilroy. The other forty or so men who showed up were not able to establish they were the "real" Kilroy. Kilroy gave his prize to his nine children to play with in their front yard.