Trees in the Chicago regional forest can contribute significantly to human health and environmental quality. The urban forest resource comprises all trees, both within and outside forested stands. This can include boulevard trees, trees planted in parks, and trees that naturally occur in public rights-of-way, as well as trees planted on private or commercial properties. Relatively little is known about this forest resource, what it contributes to society and the economy, and the value of its contributions. This book focuses on the urban trees and forests in the Chicago region and assesses the effects and values of these forests.