The Shannon River (E^voo – Senos) features on Ptolemy’s map of Ireland (c. 150 a.d.), which also locates a tribe near Limerick, the Gangani, not subsequently known. The later settlement developed on King’s Island—then known as Inis Sibtond—the Erainn dynasty having a branch known as Erainn of Inis Sibtond, who may have controlled it about the beginning of the historical period. The battle at Luimnech (c. 575 a.d.) may refer to a location in Connacht, the earliest references to the northMunster Luimnech occuring in a law tract (c. 700 a.d.), where the estuary itself is intended; also, an early saint’s life speaks of an island "in that sea called Luimnech," and a ninth-century tale mentions Loch Luimnig (loch here meaning "estuary").
By the sixth or seventh century, the subject peoples of Munster were known as Deisi (vassals). The land of In Deis Tuaiscirt (the northern vassalry) straddled the Shannon near Limerick. A branch, the Ui Caisin, included Luimnech among its lands. A parallel offshoot, Ui Tairdelbaig, established the kingdom of Dal Cais across the Shannon (from which Brian Boru descended). The introduction of Christianity to the Limerick area is associated with Ui Tairdelbaig, the city’s patron saint, Mainchm son of Setna (St. Munchin), being a member of the dynasty, said to have been granted land on Inis Sibtond by Ferdomnach of Dal Cais to found a church (possibly the site of the modern St. Munchin’s church).
Viking raiding parties used the Shannon from the 830s, attacking churches along its route and, by mid-century, had established a settlement at Limerick, building a fortress on Inis Sibtond. It was a very strategic site, protected from the west by the Shannon and elsewhere by the Abbey River. The Viking rulers of Inis Sibtond had access to the very interior of Ireland, making Limerick, after Dublin, perhaps the most important commercial center in the country. Tomrar son of Elge, "Jarl of the Foreigners," based himself there in 922 to ravage the Shannon valley. By this time the Norse kingship of Limerick, drawn from a Hebridean dynasty, had emerged as a regional power, challenging Dublin for supremacy of the Irish Scandinavians.
As Dal Cais strengthened its position in north Munster around the mid-tenth century, the potential of Limerick was recognized. In 967, Brian Boru’s brother Mathgamain slaughtered the Limerick Norse in battle, burning their ships, plundering Inis Sibtond and its fortress (dun), and the Norse king Ivar was temporarily expelled. In 972, the Norsemen were driven out of Inis Sibtond and the dun was set on fire. The subjugation of the Limerick Norse was completed by Brian Boru in 977, when he slew Ivar and his sons on Scattery Island, after which the Dal Cais controlled Limerick and maintained a fleet on the estuary. Brian may have selected Inis Sibtond as one of his bases, if it is the Inis Gaill Duibh (Island of the Black Foreigner) where he built a stronghold (daingen) in 1012.
In 1016, the Dal Cais royal poet Mac Liag died at Inis Gaill Duibh and the city featured in the struggle in the 1050s between Donnchad son of Brian Boru and his nephew Tairdelbach Ua Briain (d. 1086). Later, Tairdelbach and his son Muirchertach (d. 1119) made the city their capital and summoned provincial kings there to make submission. Muirchertach refortified the island defences in 1101 by demolishing the Grianan of Ailech, royal site of the northern Ui Neill, and commanding his army "to carry with them, from Ailech to Limerick, a stone for every sack of provisions which they had" (AFM). Like his great-grandfather, Muirchertach had a Shannon fleet, probably based in Limerick, and used it to maintain suzerainty over the rival ports of Dublin and Waterford.
Under Tairdelbach and Muirchertach, Limerick emerged as a major center of the church reform movement. In 1111, its first properly consecrated bishop, Gille (Gilbert), presided as papal legate over the Synod of Raith Bressail, which drew up a fixed territorial diocesan scheme. Gille tells us that he spent some time, and perhaps studied, in Rouen, where he met the future St. Anselm of Canterbury. When he wrote from Limerick to Anselm about 1107, he sent him twenty-five pearls, presumably obtained from local oyster harvesters. Trade and fisheries were Limerick’s staples, and the wealth its masters could obtain from these is suggested by the goods which Tairdelbach Ua Briain (d. 1167), nephew of Muirchertach, escaped with from the town in 1151: besides the drinking-horn of Brian Boru, he made off with "ten score ounces of gold and sixty beautiful jewels" (AFM).
At the time of the Anglo-Norman invasion, Domnall Mor Ua Briain, son of Tairdelbach (d. 1167) was king of Thomond and ruler of Limerick. He rebuilt St. Mary’s cathedral in the 1170s and may have introduced Continental religious orders to Limerick, being credited by Sir James Ware as founder of St. Peter’s priory for Augustinian nuns just outside the city walls. Domnall Mor defeated the Anglo-Normans at Thurles in 1174, but they advanced on Limerick in 1175 in alliance with the high king, Ruaidrf Ua Conchobair. Giraldus Cambrensis describes how the attackers "found that the river was swift flowing and deep, and formed an intervening obstacle which they could not cross." The "Song of Dermot" also records that the city "was surrounded by a river, a wall, and a dyke (fosse), so that no man could pass over without a ship or a bridge, neither in winter nor in summer, except by a difficult ford."
Nevertheless, the Anglo-Normans took the town, but within two years were forced to abandon it again to Domnall Mor Ua Briain. Although nominally granted by Henry II to Philip de Briouze in 1177, the Anglo-Normans did not regain Limerick until after Domnall’s death in 1194, infighting among the Uf Briain facilitating their return. William de Burgh held Limerick prior to 1203, briefly detaining Domnall’s son as prisoner there, but King John revived the de Briouze interest, granting the lordship of Limerick to William de Briouze (though it was subsequently withdrawn). John may have ordered the construction of the castle that still bears his name, although no evidence to that effect exists (and he never stayed there), and, in order to penetrate west of the Shannon, the castle was followed by construction of Thomond Bridge.
There was no bridge where the later Baal’s (or Ball’s) Bridge stood at the time of the Anglo-Norman arrival, but it was built soon afterward, and became a prominent landmark. A grant of King John to Thomas fitz Maurice mentions "a burgage near the bridge on the left, at the entrance of the vill towards the north, within the walls of Limerick." In 1340, Edward III ordered funding for a bridge, possibly that which survived until its replacement in 1830. The origin of the name is unknown; one theory is that baal comes from the Irish maol (bald), and applied to bridges lacking parapets. Speed’s map of 1610 calls it "The thye bridge," presumably because it linked the "English" and "Irish" towns on either side of the Abbey River.
The King’s Island site comprised "King John’s Castle" and a walled enclave surrounding it, which in the later Middle Ages became known as Englishtown, the rest of the island being less settled, the castle constable having grazing rights while the citizens also used it for recreation. The adjacent fisheries were highly prized and consequently controversial, especially the competing claims to a share in their profits. The Black Book of Limerick records an inquisition (1200-1201) by a jury of 36 inhabitants (12 Irishmen, 12 members of Limerick’s old Norse community, and 12 new English residents) that found that the archbishop was entitled to "half of the fishery of Curragour, and the land of the mill on the water near the walls of the city, and altogether a tenth of all the fish which are caught by the fishermen of that city." Upriver from Curragour was the salmon fishery of Laxweir, which, as its Norse name indicates, existed since Viking times.
The mill recorded in 1200-1201 is probably that marked on the map of Limerick drawn circa 1590 (TCD MS 1209/58), named Thomas Arthur’s Mill from one of the city’s leading merchant families. The map has another mill called Queen’s Mill, which may also date from King John’s reign, when the bishop was compensated "for the damage done to him by the construction of the King’s mills and fisheries at Limerick."
The priory of SS Mary and Edward, for Augustinian "Crutched Friars," apparently existed by 1216, and the Knights Templars and Hospitallers both had houses there, while the Franciscans were introduced by the de Burgh family circa 1267. There was a hospital of St. Mary, a poor-hospital of St. Laurence, and also a leper hospital in the city. Donnchad Cairbreach Ua Briain (d. 1242), a younger son of Domnall Mor, although not ruling Limerick, is said by Ware to have founded St. Saviour’s Dominican priory, where he was buried in 1242.
One of his successors, Brian Ruad (d. 1277), apparently reasserted lordship, and the English hosted "to Limerick against Ua Briain" in 1271 (AI). His grandson Tadc Luimnig (d. 1317, AI) may have been born in the city. Fighting around Limerick in 1313 appears to have involved rival Ui Briain factions, but the city was in English hands when in 1370 it was sacked and burned by the Irish of Thomond. In 1466, Tadg Ua Briain of Thomond placed on a formal basis the "black rent" long claimed by his dynasty from the city. Generations of neglect by the Dublin-based administration of the Lordship of Ireland—its energies concentrated on defense of the Pale—had left Limerick in a greatly weakened state by the end of the medieval period. Although the city’s merchants fortified Irishtown in walls stronger than Englishtown on King’s Island, and St. Mary’s cathedral thrived on their patronage, the deficiency of royal government saw even its once great castle reduced to what contemporaries described as a ruin.
