SIOUX FALLS, S.D. — A small patch of prairie sits largely unnoticed off a desolate road in southwestern South Dakota, tucked amid gently rolling hills and surrounded by dilapidated structures and hundreds of gravesites — many belonging to Native Americans massacred more than a century earlier.

The assessed value of the property: less than $14,000. The seller’s asking price: $4.9 million.

Tribal members say the man who owns a piece of the Wounded Knee National Historic Landmark on the Pine Ridge Indian Reservation is trying to profit from their suffering. It was there, on Dec. 29, 1890, that 300 Native American men, women and children were killed by the 7th Cavalry in the final battle of the American Indian Wars....