Pipestone national monument
The Three Maidens are actually granite glacial "erratic's" moved thousands of years ago to Pipestone National Monument by the glaciers originating in Canada.
History of the park
The Pipestone quarries are a significant site for many American Indian cultures. The site is still considered a sacred place by many who come to quarry or visit. As in the past, it is a place treated with reverence and respect. The National Monument was established by an act of Congress on August 25, 1937, and the establishing legislation restored quarrying rights to the Indians.