The Last Bridge, also known as the Bridge of Mitheithel or the Bridge of Hoarwell, was an ancient stone bridge that carried the East Road over the River Hoarwell (Mitheithel), about a hundred miles east of Weathertop and roughly the same distance west of Rivendell. Its three great arches crossed the river at the bottom of a short steep slope and to the east the land rose again into the wooded hills of the Trollshaws. It was the only practicable crossing point south of the river's sources in the Ettenmoors.
How ancient the bridge was is unknown. It may have been as old as the East-West Road, which possibly dated to the First Age or or it may have been built or improved by the Númenóreans in the Second Age. In the Third Age, the bridge was within the bounds of the realm of Arnor, and then on the border of two of its three successor realms, Cardolan and Rhudaur, and probably these two realms kept up the maintenance of this strategic structure.
In T.A. 2941, Thorin and Company passed over the bridge on their way to the Lonely Mountain. After the crossing one of the ponies bolted back into the river and its load of food was lost. This loss of provisions and the dwarves' inability to ignite a fire in the wind and rain led to the encounter of Bilbo Baggins and his companions with the unfriendly trio of trolls.
On 11 October T.A. 3018, three Black Riders were guarding the bridge against Aragorn and the hobbits on their journey to Rivendell. Their plan was foiled by Glorfindel, who drove them away and left his token, a green beryl, on the Bridge. Two days later, Aragorn found the beryl, took it as a sign that the bridge was safe, and led the hobbits over it.