Cedar River trestle, 203 feet high, 843 feet long, photography of lumberjack and logging photographer Darius Kinsey

Found on http://www.highestbridges.com/wiki/index.php?title=File:CedarRiverTrestle3.jpg&limit=500

And it seems they were made like this:

Found on http://www.dpreview.com/forums/post/50948934

But have you seen a yarding donkey?

Photo by Clark Kinsey, 1930.

Found on http://www.rustygrapple.com/Machinery.html