With the creation of Google Maps and the other main web mapping services there has been an increased interest in actually using these tools to perform real spatial analysis. Yet while interest may be strong, knowledge of how spatial analysis is conducted is sketchy at best for most people. Interestingly, it was in the mid to late 1800's that geography was first used to study problems such as disease epidemics, poverty and crime, fields that now use GIS extensively.
One of the best early examples of using geography to help understand a disease epidemic are the maps of John Snow, produced in the cholera epidemic in London in 1854. These maps have been reproduced numerous times as an example of how simple mapping of cholera deaths can reveal locations of disease origins. In the case of the London outbreak the origin was a water pump. Once the pump was shut down the epidemic subsided greatly. While Snows maps would be considered somewhat crude by today's standards they have been re-created through the years to provide more detail.
One of the first examples of Choropleth mapping ever used was by the French social statistician Andre Michel Guerry in 1833 to map property and personal crime rates in france. These maps were groundbreaking for their time as they told the story of crime for a country in an easy to understand format. Moreover, they provided a method for visualizing clusters of high crime, something that Criminologist and Police agencies still spend a lot of time doing.
The final example of early spatial analysis is provided by Charles Booth, a businessman who became greatly interested in the social problems of Victorian London. In 1889 Booth and his assistants painstakingly mapped the distribution of income at the street level. The detail on Booths maps is so good as to provide almost house by house distinctions. One issue with the maps is that the color scheme used by Booth was extensive (8 classes) and the colors themselves are not very distinctive, making the groups blur sometimes.
Overall these three great examples point out the power of spatial analysis to tell a story of social problems in a manner that pure statistics cannot. Specifically, maps provide the power of visualization of patterns in their real setting as opposed to abstract data.