Thanks Pedro - that image was generated by PeerJ staff simply to illustrate the homepage (i.e. it is not necessarily the same data that was used in the paper).
The image was generated at this page
The lung cancer incidence data used in the paper was for 2005-2009. State cancer profiles has since been updated to 2007-2011 incidences. Unfortunately, the 2007-2011 release lacks county-level data for Nevada, Minnesota, and Kansas. For the later two states,
%%Data not available because of state legislation and regulations which prohibit the release of county level data to outside entities.%%- Daniel Himmelstein •