The three kilns date to the 19th century, remnants of an industry that burned limestone into lime and shipped it to cities along the Ohio River to make bricks, mortar and plaster.

Preservationists and Indiana officials thought enough of the structures, built into hillsides near Utica, Ind., to protect them from the Ohio River Bridges Project as part of a massive preservation plan.

But the kilns are now at risk -- part of a dispute over who is responsible for keeping them intact and whether the project's massive preservation plan really ensures their survival.