I hope you don't think 'oh, no, not another covered bridge.' I ran across these while going through my actual photos and scanned them in. I tried to reduce their size...I am not sure why sometimes my software will reduced scanned images just fine and others I cannot. Well, I can but I don't get the expected photos...it is too weird and too long to try to go into detail. And I spent too much time with the clone tool to go back and scan them in at a smaller size.
I tried using my software to get a better photo out of this but I couldn't. It is the Narrows Bridge in Parke County, Indiana. It was built in 1883 by J.A. Britton, and retired from use in 1960 when a regular two lane paved bridge was built next to it. The bridge is still sound.
I thought I would show some of the structure of the bridge since I had these photos that really show it well. This is the bottom of it--can you imagine building this in 1883? I really wonder what kind of tools they had to accomplish this.
The picture above as well as the two below show the inside of the bridge. I love to imagine the sound of a horse walking through it...I am not sure how long the bridge is...if I find out later tonight I will edit and add the length here.

There are different views as to why bridges were built covered, some of the reasons being:
1. to protect the wood structure of the bridge. In ways I tend to think this might be the right one.
2. I have heard it thought it was to keep the bridge from getting iced over in bad winter weather. I think that is even sound reasoning.
3. still another reason is to keep horses from being scared when walking across them....
I know I have read of other reasons but right now these are the ones that stick in my mind.