Early in the First Age some of the Eldar left the Great March and settled in the lands east of the Misty Mountains. These elves became known as the Nandor and later the Silvan Elves. By S.A. 1200 Galadriel had made contact with an existing Nandorin realm, Lindórinand, in the area that would later be known as Lothlórien, and planted there the golden mallorn trees which Gil-galad had received as a gift from Tar-Aldarion.
The culture and knowledge of the Silvan elves was considerably enriched by the arrival of Sindarin Elves from west of the mountains and even the Silvan language was gradually replaced by Sindarin. Amongst these arrivals was Amdír, who became their first lord, as well as Galadriel and Celeborn, who also crossed the mountains and the Anduin to join these southern Nandor after the destruction of Eregion during the War of the Elves and Sauron. Ultimately, Amdír led an army out of the forest as part of the Last Alliance of Elves and Men, just as Oropher, another Sindarin lord, led the Silvan Elves of the north in the same victory over Sauron, so it can be assumed that both northern and southern woodland realms had been founded by then.
With the gradual return of Sauron's malign influence to the forest east of Anduin, the northern Silvan Elves led by Thranduil son of Oropher (and father of Legolas), moved even further north to escape it, and those of the south returned west across the Anduin, although without their last Sindarin lord Amroth son of Amdír, who departed to Edhellond after his lover Nimrodel had fled there.
It was later revealed that Galadriel's Ring enriched the land by preserving its flora from death and decay, and in wielding it she created a powerful ward against all creatures of evil intent: in fact the only way that Galadriel's Lothlórien could have been conquered by Mordor is if Sauron himself, the master of all the Rings of Power, had come there.
Following the departure of Galadriel for Valinor at the beginning of the Fourth Age, the Elves of Lothlórien were ruled by Celeborn alone, who led them across the Anduin to found a new, larger realm, East Lórien, centred around Amon Lanc. By the time of the death of Queen Arwen, Celeborn and Galadriel's granddaughter, Lothlórien itself was deserted.