Here's a really fun map that plots out where UFO sightings are seen the most across the US of A. Made by John Nelson of IDV Solutions, it shows where sightings are seen the most in relation to the area's population, compares the popularity of different types of shapes of UFO across the years (1970's had disk shaped, 2013 is all about the fireballs) and when UFOs are seen the most (summer nights!).
Of course, as is the case for any observation data, there is a strong tendency towards echoing a population map. This is certainly the case with this sighting data, as well. In order to visualise the actual sighting phenomenon, I needed to normalize by the underlying population. The first, more prominent map shows a simple ratio of the sightings by population. A per-capita approach. The second, smaller and slightly more complex map, shows a bi-variate mapping of sightings in the colour dimension (dark slate for low-sightings and bright green for high-sightings) and population density in the opacity dimension (denser populations are more transparent). The result is a map that is more nuanced regarding the problem of variable populations and area sizes.