I used to go to Savage Mills three or four times a year, but it's a husk of what it once was. A lot of the vendor spaces are empty now. Haven't been down there for a couple years, but I saw the zip-line behind the parking lot last time out.
The bridge is a Bollman truss. Wendel Bollman was a cool dude, a self-taught engineer. Built a bunch of bridges while working for Latrobe and the B&O (most famous one crossed the Potomac at Harper's Ferry...must have been a half-dozen spans in length, at least). He left the B&O to found his own company, Patapsco Bridge & Iron Works, in Baltimore. Later he did a short stint as President of the Western Maryland Railroad. Eventually cast and wrought iron construction fell out of favor for bridge components and Bollman's business began to suffer. The bridge at Savage Mills is, I believe, the only remaining example of a Bollman truss.
One of his small road bridges is preserved at Union Mills homestead a few miles up the road from me:

Healey