Clarification: Both the Clark's Trading Post bridge, and the WW&F Trout Brook Bridge are Howe Truss Bridges that are covered. Both are now in active railroad service. For a time, Clark's claim was true; our bridge was out of active railroad use for many years.
One common misconception is that the Trout Brook bridge is not a covered bridge. It is very much a covered bridge, as the sides are covered - but the Trout Brook bridge does not have a roof. The purpose the "covering" of a covered bridge is to protect the trusses - which can be accomplished by using a roof or not. This is known as a "pony truss" - where the trusses are shorter than the traffic the bridge is designed to carry. Only 5 or 6 covered pony truss bridges remain in the US; some use the Howe design, a few use a different design that I don't recall the specifics of right now.