Mapping can be a form of data visualization. Maps need not be used for navigation. This is what the Congressional elections history project is — data visualization. It has an argument embedded in the presentation, that Congress is a co-equal branch of the federal government and our use of presidential election data and maps must be matched by use of Congressional election data. Even moreso, it has the idea at its base that Congressional political dynamics are different from presidential/national political forces. Thus, a landslide win for Lyndon Johnson looks far more mixed at the Congressional level, and there are regional and local geographies at play in those election results. At the top, the House results; at bottom, the electoral college results for 1964:
Continuing with this idea of data visualization, there is one major figure in thought on data visualization: Edward Tufte. His work The Visual Display of Quantitative Information is THE classic text. He has moved onto other matters, and Nathan Yau has succeeded Tufte as the leading exponent of data visualization. Yau recently illustrated some problematic practices in data visualization on his site, Flowing Data. This might be a site worth checking out more regularly to keep up on this discussion.