The Dúnedain of Gondor were the Edain descended from the Númenórean colonists (and from their noble kin who escaped the destruction of Númenór in SA 3319) who settled in the southern land of Gondor throughout most of the Second Age.
Before the Downfall of Númenor, the region that would become Gondor was home to many Númenórean colonists, who either mingled with the indigenous Middle Men if they were friendly, or dispersed them into Ras Morthil, Dunland, and Drúadan Forest. The land on which Gondor was founded was more fertile than the more northerly areas of Middle-earth, and so it already had a fairly large population and settlements, including a well-established haven, Pelargir, founded by the Faithful Númenóreans in the year 2350 of the Second Age.
Exiles of Númenor
The refugees from Númenor led by Isildur and Anárion were given a warm reception upon their arrival by those Númenórean colonists. Those north of the river Anduin accepted Elendil 's claim to kingship over them, being an heir of the Faithful Lords of Andúnie. The Dúnedain of the South were the descendants of the Exiles of Númenor who settled in the southern lands of Middle-earth and founded the southern kingdom of Gondor. Their first independent King was Meneldil, the nephew of Isildur, whose line ruled over Gondor for more than two thousand years. Unlike their cousins in the North, the Dúnedain of the South maintained their realm even after the loss of its Kings, and it survived under the rule of the Stewards until the time of the War of the Ring, when the Kingship was restored.
Dol Amroth was entirely populated with Dúnedain of the South throughout the Second and Third Age.