Two self-described "grammar vigilantes" from the East Coast are being banned from national parks for a year and fined $3,035 after altering a historic sign at the Grand Canyon.

Jeff Michael Deck, 28, of Somerville, Mass., and Benjamin Douglas Herson, 28, of Virginia Beach, Va., pleaded guilty to conspiracy to vandalize government property and were sentenced in federal district court in Flagstaff on Aug. 11 after being charged in April. As part of a countrywide hunt for writing errors, the members of the so-called Typo Eradication Advancement League added an apostrophe, removed an apostrophe and added a comma in a sign describing the Hopi Room in the Desert View Watchtower, which is a National Historic Landmark.

The men used a product similar to Wite Out and a black marker.

The two later posted their activities to a Web site. The Web site was reported to National Park Service personnel.

The Web site had a photo of the sign, a narrative of defacing the sign, and a photo of a man at the Canyon rim holding a plastic bag of markers.

The hand-painted sign is likely from the 1930s or 1940s, and is rare, the Park Service said.