Hello all, thanks for the replies. I did speak with the town of Fremont Historian and he can't remember the line going past the depot during the Spaulding and Frost days. He knows the family that owns the farm adjacent to the bridge and to the best of his knowledge, they did not use it to move livestock from one side of the river to the other.
He did say that it was a covered bridge up to the 1930s when it was replaced by an iron bridge, the same one that exists today but he's no idea why it was left and others were removed. He thought it might be because the state, which owned the right-of-way, might want to re-activate the line. But I pointed out that other bridges had been removed and the section from Epping to Barrington had been paved over.
So, it's still a mystery. He did tell of a photo a local resident took in 1917 of 3 black soldiers guarding the bridge that he has in his possession. As strange as it may sound today, the US Government was worried about German sabotage during WW 1. I did manage to find it online and It's also in a book about covered bridges in NH.
BTW, does anyone have any pictures of it, iron or covered, they could share?