Something of the scale of these woods can be gleaned from accounts of travelers and pioneer settlers.
Mature hardwoods can grow so tall that naturalists have to use binoculars to see their leaves.
The French moved up and down rivers aboard dugout canoes made from single logs of cottonwood or sycamore up to 40 feet long. A Shumard red oak in Beall Woods is the biggest such tree in the United States, and Illinois hosts hickories that are 400 years old. Some cypress tress in the southern Illinois bottomland forests have been likened to sequoias, being as many as one thousand years old. During most of the human occupation of Illinois, the forests constituted an essential part of the domestic economy. The diversity and quality of forest food is high, although supplies vary more than in other ecosystems.