Tristifer, the Fourth of his Name, King of the Rivers and the Hills, ruled from the Trident to the Neck thousands of years before Jenny of Oldstones and her prince, in the days when the kingdoms of the First Men were falling one after the other before the Andals. He was called the Hammer of Justice, and the singers say that he fought a hundred battles and won nine-and-ninety. When he raised his castle, now a ruin known only as Oldstones, it was the strongest in Westeros (III: 520)
Tristifer IV was killed in his hundredth battle, when seven Andal kings joined forces against him. His son, Tristifer V, was not his equal, and soon the realm was lost, and the castle, and then the line. With Tristifer V died House Mudd, that had ruled the riverlands for a thousand years before the Andals came (III: 520)
Old King Andahar and his two-headed water horse is mentioned. The "water horse" is a great flat-bottomed oared boat that crosses the Trident at Lord Harroway's Town, controlled by Lord Roote (III: 538, 539. SSM: 1)
Lord Commander Tristan Mudd of the Night's Watch was among a handful of Lords Commander who have been more proud and ambitious than wise, nearly destroying the Watch when they forgot their vows (III: 612)
Snow in autumn is very rare (III: 915)
The smallfolk in the wetlands northwest of Maidenpool are shy and live quite apart from one another. They live in huts made of mud and straw, or in houses built on rickety stilts with rope ladders to be able to enter them above the dunes. They fish in leather coracles or collect clams (IV: 371-372, 374)
3lackfyre rose in rebellion, and the black iron dragon was cut down by Lord Darry, who was fiercely loyal to King Daeron II. The inn became known as the River Inn, as the river was right up against it and some of the rooms were built over the water. The river changed its course in the 220th or 230th year (IV: 548)
Wine is made in the riverlands (TMK: 679)
The riverlands are rich, fertile, and populous (SSM: 1)