[7] Audubon Society and its supporters successfully prevented Plum Island from being developed into a resort area and upscale condominiums.

After acquiring the island, the Illinois Audubon Society gained the support of Living Lands and Waters, a river cleanup group led by Chad Pregracke.

LL&W removed unsightly buildings and structures from the island during a month-long effort, hauling away the debris on their barge.

The Illinois Environmental Protection Agency provided a small grant to help fund removal of debris, old cabins and a boat from the island.

[9] The Illinois Audubon Society wanted to save the island for the eagles, to preserve the scenic view from Starved Rock, and to protect the Native American archaeological sites which are there.

[10][1] Two juvenile bald eagles were rescued on June 2, 2011, after their nest fell 85 feet in a windstorm at the Mooseheart facility near Batavia, Illinois.

They were rescued and raised by the Flint Creek Wildlife Rehabilitation organization and were released back to the wild at Plum Island to blend with the current eagle population.

[11] Excavations at the site yielded prehistoric and Historic artifacts, pit features, burials, animal bone and plant remains.

[11] The firepits appear to correspond to what has ethnographically been described as "macoupin roasting pits" by the early French explorers Deliette and LaSalle and described from the Zimmerman site.

[12] Tubers of Nelumbo lutea have been recovered from similar roasting pits at the Elam[13] and Schwerdt[14][15] sites on the Kalamazoo River in western Michigan; and tubers of the white water lily (Nymphaea tuberosa) have been recovered from roasting pits at the Griesmer site in northwestern Indiana.

"Grim reminiscences of the destruction of the Illinois Indian town and the massacre of some of the inhabitants on the spot were uncovered in the first year of exploration, in the form of charred wood and unburied skeletons strewn about on the old site of the village just a few inches below the present surface of the plowed field."

The main species present were fish (especially channel catfish and freshwater drum), deer, elk, raccoon, beaver, dog, turtle, snails and fresh water mussels.

Middle Woodland cultures are characterized by their large burial mounds, some of which are still visible today; as well as their distinctive pottery forms, ceremonial practices, agricultural activities, and widespread trade networks.

This pottery is characterized by shell tempered, globular vessels with cordmarked surfaces and straight to excurved rim profile.

Decoration, when present, consists of incised and trailed lines, punctates and finger impressions, combined to form arches and festoons.

This component apparently lasts until the Protohistoric or early Historic period based on the European trade goods present at the site.

[11][23] The trait list of Plum Island was compared to that of other sites in Illinois to gauge regional relationships in material culture.