Three groups are threatening to sue if state and federal officials don't return West Virginia's Blair Mountain to the National Register of Historic Places.
The National Trust for Historic Preservation, Sierra Club and Ohio Valley Environmental Coalition told the National Register and the state Division of Culture and History to fix the problem or they'll face litigation by September.
Neither agency had an immediate response Friday.
The site of a bloody battle in southern West Virginia over union organizing in 1921 was briefly added to the register last year. It was removed after the number of objecting property owners was corrected from 22 to 30 out of 57.
Federal rules bar listing an area on the register if a majority of area property owners oppose it.
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