Today on Twitter Colleen Greene tweated this great link for old maps.
You enter in the location and are shown some online historical maps that cover that area. You can then click on the maps to see boundaries and place names from different time periods.
This site is very useful for genealogy research! I checked out several locations and each time there were several maps to choose from. For example, see Sheffield, England.
Try it with any location, I expect you will be pleased with the results. I found this site useful enough to include in my Genealogy Resources Worldwide page which I am slowly building.