The river is sourced from an underground lake at the Black Mountain emerging at the surface from Llygad Llwchwr which translates from the Welsh as "eye of the Loughor".

On the south side of the inlet, the gathering and processing of cockles (Cerastoderma edule) contributes significantly to the economy of the villages of Crofty, Llanmorlais and Penclawdd.

The estuary is also an internationally important location for waders and other wildfowl, which has led to demands from cocklers for the control of oystercatchers (Haematopus ostralegus), which feed on cockles.

Llanelli, on its north shore, was noted for its tinplate industry, whilst Penclawdd, on the south side, smelted copper from ore shipped in from Anglesey.

This vigorous grass has since spread in a wide band all along the south side, forming the basis of a salt-marsh supporting the grazing of sheep, ponies and cattle.

Persistent rumours that anthrax biological warfare shells were tested against sheep in the estuary were finally substantiated in a reply to a parliamentary question from the late Tony Banks in January 1987.

[4] In the 1960s, the Ministry of Defence proposed to move its main artillery and explosives testing facility at Foulness, at the mouth of the River Thames, to a site between Burry Port and Kidwelly, which was already used in a very sporadic way as an air-to-ground rocket range.