The River
From Tolkien Gateway
The River, also known as Baranduin was by no means the widest or longest of the rivers of Middle-earth, but it was the only large river to flow near the Shire, whose eastern border it formed. The Hobbits who lived there called it the 'Brandywine', but it was sometimes known simply as 'The River'. This form appears especially in the phrase 'from the Downs to the River', an expression of the Shire-hobbits that refers to the Far Downs and the Baranduin, the western and eastern borders of their land.
