This map shows the percentage of each county’s civilian population (aged 18+) who have veteran status. For Census data, as shown here, the term “veteran” is based on the Department of Veteran Affairs’ definition:

A veteran is someone 18 years and older (there are a few 17-year-old veterans) who is not currently on active duty, but who once served on active duty in the United States Army, Navy, Air Force, Marine Corps, or Coast Guard, or who served in the Merchant Marine during World War II. There are many groups whose active service makes them veterans including: those who incurred a service-connected disability during active duty for training in the Reserves or National Guard, even though that service would not otherwise have counted for veteran status; members of a national guard or reserve component who have been ordered to active duty by order of the President or who have a full-time military job. The latter are called AGRs (Active Guard and Reserve). No one who has received a dishonorable discharge is a veteran.

http://www.census.gov/prod/2011pubs/12statab/defense.pdf

Based on this definition, military personnel on active duty are not counted as veterans, but several paths of active service qualify people for veteran status. As such, military bases will have a notable effect on this map, though not as significant as they could (if those on active duty were counted). For each of the top counties list, I included the names of the largest military installations in the respective county.

Data source:

http://factfinder2.census.gov/faces/nav/jsf/pages/searchresults.xhtml (table S2101)