Shortly after it was established in 1970, the Environmental Protection Agency undertook a project called "Documerica," which paid freelance photographers across the country to document the environmental and human conditions of the country. All told, more than 15,000 images were collected for the project, and then more or less forgotten until last year, when the EPA and National Archives rediscovered the photos and put out a global call for people to submit matching images from the present day.
An exhibit of original images are in Dallas right now through August 14 on the seventh floor of Fountain Place downtown. You can browse through the collection online, which is worth doing. The photos aren't always what you expect from the EPA, like the dapper gentlemen in downtown Dallas you'll see below, or the two girls smoking pot in Leakey, Texas above. Taken with their permission, of course.