Which National Park has the highest attendance?

Hello Carmencitaa,

With over 9 million visitors per year
  Great Smoky Mountains National Park

Sources:
  http://www.npca.org/across_the_nation/ten_most_endangered/
Scroll down to #4 which indicates this is the most attended.

  http://www.nps.gov/grsm/
Confirmation on the number of visitors on the National Park Service
web site (but does not indicate it is #1 in attendance).

For comparison:

  http://www.nps.gov/grca/grandcanyon/quicklook/nationalpark.htm
Grand Canyon at 5 million per year.
  http://www.nps.gov/yose/planning/vol14/1.htm
Yosemite at 4 million per year.
  http://www.nps.gov/yell/press/04118.htm
Yellowstone at 3 million per year (though another page indicates 5
million visitor days).
  http://www.nps.gov/transportation/alt/documents/airnoise.pdf
About 300 million overall visiting the National Park Service.

Search phrases for more information:
  million visitors site:nps.gov
  million visitors national park

  --Maniac

Helpful ... thank you very much.