Ober's Island, One of the Review Islands on Rainy Lake, bounded on the south by The Hawk Island and on the north by The Crow Island. These islands are located seven miles east of Ranier, Minnesota, three miles west of Voyageur National Park, and one mile south of the international border of the United States of America and Canada. The legal description of Mallard Island is Lot 6, Section 19, T-17-N, R-22-W, Koochiching County, Minnesota, Ranier, Koochiching County, MN

Significance: The Ernest C. Oberholtzer Rainy Lake Historic District is nationally significant under national register evaluation criteria B, recognizing the contributions of Ernest Oberholtzer as a pioneer in wilderness conservation. He was a conservationist, explorer, and wilderness philosopher of the Rainy Lake area. His legacy is associated with the Quetico-Superior Council, of which he was a founder (1928) and president; the President's Quetico-Superior Committee, on which he served from 1934-1968; as an articulate voice of authority in the struggle to preserve wilderness character in the border lakes region along the international boundary between the United States and Canada; and as a founder and officer (1937-1967) of the Wilderness Society."

Ernest Carl Oberholtzer was born February 6, 1884, in Davenport, Iowa, and died June 6, 1977, in International Falls, Minnesota. He lived most of his adult life on Mallard Island in Rainy Lake near Ranier, in northern Minnesota.

Oberholtzer was educated at Harvard University, receiving a broad liberal education, graduating with a Bachelor of Arts degree in 1907. During his senior year, Oberholtzer studied landscape architecture under the tutelage of Frederick Law Olmsted Jr. He then continued an additional year at Harvard in the newly established school of landscape architecture under the tutelage of James Sturgis Pray.

The Ernest C. Oberholtzer Rainy Lake Historic District nomination did not document nor analyze the cultural landscape of Mallard Island. Yet the cultural landscape of Mallard Island remains as a monument to the genius of Ernest Oberholtzer in the area of landscape architecture. This island is significant under national register evaluation criteria C, as a distinguishable entity whose components may lack individual distinction, but its distinctive characteristics are of a type, period, and construction that represent the work of a master and possess his high artistic values.

The cultural landscape of Mallard Island is significant at the national level as embodying the type and period of a rare remaining example of a personal estate created by a student of the world's first professional graduate course in landscape architecture education. It is significant at the state level as embodying the type and period of rustic landscape architecture associated with the National Park Service, Civilian Conservation Corps and state recreational development in Minnesota. Mallard Island also is significant at the local level as embodying the historic context for tourism and recreational development in the northern border lakes from the 1880s through the 1950s.
Survey number: HALS MN-6
National Register of Historic Places NRIS Number: 00000570