The road is South main St, route 527. If you come from South Bound Brook you cross the Raritan, then the Port Reading branch and immediately on your right is a driveway to some company or trucking warehouse. That driveway now covers most of the original bridge deck and paving and when the building was put up most of the original stream bed was obliterated and the fill dumped in to the stream bed covered most of the bridge. What you see now, on the southern side of the bridge, is the bottom of the curved stone arch which served as the bridge piers but the rest of the bridge is still intact under the ruble. It seems to have been a substantial structure and it had to be as the Swift Stage Coach Company used it as part of its regular route from the Delaware Valley, West Jersey to the Raritan Valley in East Jersey. During the Revolution both armies regularly used this route and it rougly parallels, and originaly was, what became US 202 whose modern roadbed was constructed in the early 20th Century. You can actually see the intact original bridge in a book entitiled Along the Old York Road by James Cawley. The photograph shows the bridge in good relief with a circa 1950 car parked along side. It was the railroad that changed the importance of the bridge and Old York Road. Some years ago I tried to interest Rutgers and the state historical society into doing something to mark and preserve the site but other than the battlefield marker a few yards from the bridge nothing has been done. Since it may indeed be the oldest man made structure in NJ that's a shame.