Viking adventurers established a settlement on an island in the River Shannon in the 9th century. They fought with the native Irish for control of the site until Brian Ború's forces drove them out in 968 and established Limerick as the royal seat of the O'Brien kings. Brian Ború finally destroyed Viking power and presence in Ireland at the Battle of Clontarf in 1014. By the late 12th century, invading Normans had supplanted the Irish as the town's rulers. Throughout the Middle Ages the two groups remained divided.
From 1690 to 1691 Limerick acquired heroic status in the saga of Ireland's struggle against occupation by the English. After their defeat in the Battle of the Boyne in 1690, Jacobite forces withdrew west behind the famously strong walls of Limerick town until the Treaty of Limerick guaranteed religious freedom for Catholics. The English later reneged and enforced fierce anti-Catholic legislation, an act of betrayal that came to symbolise the injustice of British rule, while Limerick gained the nickname 'Treaty City'.
During the 18th century the old walls of Limerick were demolished and a well-planned and prosperous Georgian town developed. Such prosperity had waned by the early 20th century, however, as traditional industries fell on hard times. Several high-profile nationalists hailed from here, including Éamon de Valera.