The Volo Bog State Natural Area is a state park and natural area in Ingleside, Illinois. It features the Volo Bog, best known for being the only “quaking” bog in the entire state to have a center that is open water.

First documented in 1921, the Volo Bog was originally known as the Sayer Bog, after the lot’s owner, George Sayer, a dairy farmer. The University of Illinois later acquired the property after the fundraising and efforts initiated by the first director of the Illinois Chapter of the Nature Conservancy, Cyrus Mark. When the bog was threatened in the late 1960s, locals established the “Save the Volo Bog” committee which led to the transfer of the property to the Illinois Department of Natural Resources.

The Volo Bog State Natural Area was established in 1970. It was later designated as a National Natural Landmark.