Pelargir was the chief city of the region of Lebennin, built where the river Sirith joined with the Great River. It was the primary port of Gondor.
Pelargir was one of the oldest cities in Gondor, founded by the Faithful Númenóreans in the Second Age. During the Third Age, it was under continual threat from the Southrons and the Corsairs of Umbar.
Spoiler warning: Plot or ending details follow.
During the Kin-strife, the rebel followers of Castamir retreated there after his death, led by his sons. At Pelargir they fought a lengthy seige against the rightful King of Gondor, before fleeing to Umbar.
During the War of the Ring, Pelargir was besieged by the Black Ships of the Corsairs, but was liberated by Aragorn and the Dead Army.
Pelargir was the first city of the Faithful Numenoreans in Exile, founded in 2350 Second Age before the birth of Gondor.
The Wardens of Pelargir are best represented by the Warriors of Numenor, as their armour showed no change from that used by the first seafarers to arrive in Belfalas.
Unlike the neighbouring fief of Pelargir, ballistae in the form of Bolt Throwers were not suited to such graceful vessels, and were instead used for defending the ports alongside Trebuchets.