The Kanawha Valley in West Virginia had one of the highest concentrations of burial mounds in North America, according to an archaeologist whose new book on the subject is set to be published July 1.

Though most have been destroyed, Darla Spencer says that more than 400 mounds have been recorded in West Virginia, and their presence was once so extensive that European explorers couldn't believe they were of Native American origin.

"Early Europeans [coming] to the Ohio Valley, including West Virginia, thought the mounds must have been built by some earlier race of people and not the ancestors of living Native Americans," Spencer said.

To determine whose hands had raised them, the Division of Mound Exploration of the Smithsonian Institution’s Bureau of Ethnology performed their first systematic exploration in the 1880s.

"The conclusion was that the ancestors of Native Americans had built the mounds," says Spencer, though stories of non-American or even extra-planetary origins are proposed by non-archaeologists on occasion.

No precious stones or metals have ever been found in mounds, though what has been found indicates the builders were by no means isolated.

"Exotic copper and marine shell items in the mounds indicate a network of trading connecting the region with the Gulf and Atlantic coasts and the Great Lakes region," she said.

Though raised as monuments, most mounds were destroyed to make room for agricultural, residential, and commercial and industrial development.

A professor of Native American studies at West Virginia University, she examines the Grave Creek Mound at Moundsville, West Virginia, and sixteen other mounds and mound groups of mounds in West Virginia in "Woodland Mounds in West Virginia."

Spencer is also a member of the West Virginia Archaeological Society and sits on the board of directors of the Council for West Virginia Archaeology.

Her earlier book on Native American culture, "Early Native Americans in West Virginia: The Fort Ancient Culture," was published by The History Press in 2016.

"Woodland Mounds in West Virginia" is published by Arcadia Publishing Co., a leading publisher of books of local history and local interest in the U.S.