A campaign by two grammar vigilantes to correct mistakes on signs across America has come to an abrupt end after they were charged with vandalism for trying to rectify a spelling error at the Grand Canyon.

The founders of the Typo Eradication Advancement League (TEAL) have been banned by a court from correcting any publicly owned signs after trying to correct one on the Desert View Watchtower that, for seven decades, has drawn attention to an “emense westward view of the Grand Canyon”. Oblivious to grammar, the prosecutors pronounced the sign “a unique historical object of irreplaceable value”.

Jeff Deck and Benjamin Herson, both 28, met in a creative writing class. The two graduates of the Ivy League Dartmouth College teamed up after Mr Deck, from Somerville, Massachu-setts, had an epiphany in the shower. Misspellings on his shower curtain inspired him to try to make a better world by travelling the nation to correct errors with a fix-it kit of magic markers and correction fluid.

A star of high-school spelling competitions, he worked on Dartmouth’s student newspaper and honed his editing skills in a temporary job at an academic publisher. He invited Mr Herson, then working in a bookshop outside Washington, to join him in a round trip of the United States.

Their goal, according to the TEAL mission statement, was to “stamp out as many typos as we can find, in public signage and other venues where innocent eyes may be befouled by vile stains on the delicate fabric of our language”.

They found and corrected 231 signs with mistakes ranging from “birthday candell’s” to a “Sweedish” berry drink and even discovered misspellings in neon lights in Las Vegas.

They quickly identified the apostrophe as America’s greatest grammatical challenge. Their pet peeve is the number of car park signs warning that vehicles will be towed “at owners expense” – without an apostrophe.

The grammar vigilantes planned to take a day off when they visited the Grand Canyon on March 28 and found the hand-rendered sign inside the Desert View Watchtower. They covered up a misplaced apostrophe and painted it in its proper place with correction fluid. They also added an omitted comma. Reading on, however, they were appalled to discover what Mr Deck described as a made-up word: emense.

The sign was painted by Mary Colter, the architect who designed the rustic 1930s watchtower and other Grand Canyon landmarks. The authorities took a dim view of what they considered “vandalism” at a site listed in 1987 as a National Historic Landmark.

Mr Deck and Mr Herson were caught after recording their exploits on their website, which was seen by the police. The two admitted conspiracy to vandalise government property and were fined $3,035 and banned from national parks or from modifying any public signs for a year.

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