Most of the bridges are former railroad trestles that were converted into walking trails. Plus there is one section of boards across a swamp and one arching wooden bridge. (The wooden bridge is leading to the World's Largest Sitka Spruce tree -- visible in the background.)
Bridges cross deep places, and wet places, and dangerous places. Think of the places you could go to while crossing one....
Photos are 3000x4000 pixels (2 of them, 12 megapixels), 2816x2112 pixels (5 of them, 5.98 megapixels), 2112x2816 pixels (1 of them, 5.98 megapixels)