In the early years of the Two Kingdoms, Arnor and Gondor were connected by a great Royal Road that ran through the wide lands of Enedwaith. On the borders of Minhiriath, the road crossed the River Gwathló, or Greyflood, at a place surrounded by fens and marshes. At the river crossing itself a Bridge was built, and a township was maintained (Tharbad, meaning 'cross-way'). Tharbad supported a garrison of soldiers and engineers to maintain the road and bridge in the treacherous landscape.

The Bridge and its roadway survived until the end of the second millennium of the Third Age. With the loss of the King of Arthedain to the north, and soon afterwards of Gondor to the south, Tharbad and its Bridge found themselves abandoned in an unruled wilderness, and soon fell into disrepair. By the end of the Third Age, the Bridge had long since collapsed to form a dangerous and difficult river-crossing: it was here that Boromir famously lost his horse as he journeyed northward in search of Rivendell.