A Window to Our Environment

Window to My Environment is a “powerful web-based tool that provides a wide range of federal, state, and local information about environmental conditions and features in an area of your choice. This application is provided by U.S. EPA in partnership with federal, state and local government and other organizations.”

It can also be used to view population densities, zip codes, congressional districts, etc.

I suggest you check it out. Below is a screenshot I took of population density in and around Downtown Dayton.