The Battle of the Trident
Robert Baratheon and Rhaegar Targaryen met in the ford with the war resting on it, and Robert's warhammer ended three centuries of dragon kings by caving in a breastplate of rubies. The rubies washed downstream for years. Whatever Rhaegar had been trying to do ÔÇö and there is real evidence he thought he was saving the world ÔÇö died in the water with him.
The fuller tale
Rhaegar came out at last, having sat out the first year of the war wherever he had been, and gathered the last royal host ÔÇö some forty thousand men, Dornish spears among them ÔÇö at the ford of the Green Fork of the Trident. Robert Baratheon came at him with the rebel army, and both sides understood that it was the last battle either would need.
The two of them found each other in the middle of the river, which is the sort of thing that only happens in songs and happened here. Robert was the larger man and carried a warhammer, and Rhaegar was a fine swordsman in armour set with rubies. It did not take long. The hammer went through the breastplate and the rubies went into the water, and men were still finding them downstream years later.
Whatever Rhaegar had been trying to do ended in the ford. Three hundred years of Targaryen kings ended with him, and the ruby ford is still called that.
The war after the battle
The Trident decided it but did not finish it. Aerys was still in King's Landing with wildfire under the city; Ned Stark's sister was still wherever she had been for a year; Dorne had lost its prince's sister and her children to what happened next and would not forget it.
Robert was crowned because he could fight and because his grandmother had been a Targaryen, in that order. He said afterward that he had won a throne he did not want by killing a man over a woman who never loved him back, and every account of the next seventeen years suggests he meant it.
Elsewhere in the wiki
 See the world as it stood in 283 AC What became of it  if an ending is written, it is here. Spoilers.
The chronicle records no ending here ÔÇö or none the maesters have set down.