Hiking and bicycling are the two most popular outdoor activities in the U.S.
Outdoor Industry Foundation
May 20, 2013, WMATA
May 20, 2013, WMATA
Tim Craig, May 21, 2013, Washington Post
Keith Laing, May 21, 2013, The Hill
May 17, 2013
May 10, 2013
April 30, 2013