Mapping the Changing Land

Among its other duties, the U.S. Geological Survey (USGS) maintains topographic maps of the country, mostly at a scale of 1:24,000. These topographic maps are detailed enough to follow even the smallest streams, calculate the slopes of hills, and identify the positions and shapes of buildings. Because most areas have been mapped several times over decades -- and some more than a century -- they are very useful for describing changes in the land and human use of the land.

Blogger/journalists at the Washington Post recently created GIFs of some maps in the Washington DC area, with a link to the entire collection.

Geographers often use their expertise in the interpretation of topographic maps as they work with other professionals to describe the historical development of places. This can be especially useful when examining the environmental history of a site to see if it is likely to contain pollution or other hazards.