I am always astounded by what can be done with geospatial data – here is a map from The New York Times that uses data from the U.S. Census Bureau’s American Community Survey (2005-9) to show the distribution of racial and ethnic groups for every city block.
During a trip to Chicago last week, I had occasion to see one of the American Society of Civil Engineers’ (ASCE) monuments of the millennium, the Chicago Wastewater System. By the end of the 19th century, Chicagoans had heavily polluted the Chicago River by dumping all of their garbage in the water, which flowed into Lake Michigan, the source of the city’s drinking supply. This caused deadly diseases such as cholera and typhus. To solve the problem, the flow of the Chicago River was reversed, sending it in the opposite direction from Lake Michigan.
Here’s a brief documentary on the reversal of the Chicago River: