title: R convert zipcode or lat/long to county
body: <p>I have a list of locations that contains a city, state, zip, latitude and longitude for each location.</p>
  
  <p>I separately have a list of economic indicators at the county level.  I've played with the <code>zipcode</code> package, the <code>ggmap</code> package, and several other free geocoding websites including the US Gazeteer files, but can't seem to find a way to match the two pieces.  </p>
  
  <p>Are there currently any packages or other sources that do this?</p>