This part of the island, owing to its inland situation, is not noticed by Ptolemy; recourse must therefore be had to the early native writers as the only source whence to ascertain its former state. From these it has been concluded that, at a very remote period, the county formed part of the territory denominated Hy Falgia, which included also those of Meath, Westmeath, Dublin, and Kildare. It was also included, together with the Queen's county, Dublin, and Kildare, under the denomination of Hy Laoighois, the chieftain of which territory resided at Dunamase, in the Queen's county. Afterwards, this territory, or, as some say, the southern part of it only, was included in the district of Eile, or Hy Leigh, comprehending also the western part of the Queen's county, and the northern part of Tipperary. That district was afterwards divided into three principalities, each under its own chieftain; one of which, forming the southern portion of the King's county, and lying westward of the Slieve Bloom mountains, obtained the name of Eile in Chearbhuil, or "the plain near the rock," afterwards corrupted into Ely O'Carroll, the chiefs of which were called O'Carroll, and under them was a subordinate dynast, named O'Delany, who ruled over a district in the south, denominated Dal-leagh-nui, or "the district of the flat country." These principalities, with the more northern parts of the present King's county, occupied by the Mac Coghlans, O'Molloys, and O'Conors, were afterwards united into one kingdom, under the ancient title of the kingdom of Hy Falgia, or Offallia, which comprehended also a part of the county of Kildare, and the lands of the O'Dempsies and O'Duins, in the Queen's county. It retained this title for several centuries after the landing of the English, and included a smaller territory, called Hy Bressail. So early as 1170, the English power was extended into this part of Ireland, though not with permanent vigour. Thus the lands of Cryngidubh were deemed in all matters of English jurisdiction to form part of Meath; the manor of Geashill, held by the Fitzgeralds, was esteemed part of the county of Kildare; and from the Black Book of the Exchequer, and divers pipe rolls, it appears that the whole of Offallia was charged with twelve knights' fees to the king as part of the county of Kildare. But as the English power declined, its laws and customs were disregarded, and under the name of West Clonmalugra, or Glenmalire, this district was for successive centuries one of the most turbulent and hostile to the Anglo-Irish government. Eastern Glenmalire, or Glenmaleiry, and Leix, were the names then given to the Queen's county, the Barrow river being the boundary between the two districts. The O'Conors were the commanding sept in Offallia; in the reign of Edward VI., uniting with the O'Mores of Leix, they spread disorder through the province of Leinster; but the lord-deputy, Sir Anthony Saintleger, aided by a force sent from England under Sir William Bellingham, dispersed them with little difficulty, ravaged their lands, drove the inhabitants into their fastnesses in the bogs and woods, where they were reduced to the last extremities by famine, and secured their subjection by building six castles in their territory. The chiefs themselves submitted, and attended Saintleger into England, where they were thrown into confinement, and their lands being declared forfeited were shared among English officers and settlers: the O'Carrols, occupying the remotest situation, appear to have been the least affected by these disastrous events. The new arrangements were completed in 1548, and procured for Bellingham the honour of knighthood and the government of Ireland. But the old Irish families did not patiently relinquish their claims and possessions. They were indefatigable in their efforts to resist what they deemed an unjust usurpation. Numbers were consequently cut off in the field, or executed by martial law; and the whole race would have been extirpated in the reign of Mary, had not the Earls of Kildare and Ormonde interceded with the Queen, and become sureties for the peaceable bebaviour of the survivors. By an Irish statute in 1551, Lord Sussex was empowered to grant estates or leases in the districts recovered from the Irish inhabitants; another, reciting their forfeiture to the Crown by rebellion, erected them into the King's and Queen's counties, so named in honour of Philip and Mary; the former comprised Ophaly, and such part of Glenmalire as lay east of the Barrow, and had for its capital the fort of Dingen, formerly the chief seat of the O'Conors, and henceforward called Philipstown. In this division was included a small portion of the county of Kildare, containing the parishes of Harristown and Kilbracken, which still, though completely enclosed by Kildare, continue to form part of the King's county. During the entire reign of Elizabeth, the desultory attempts of the natives against the English forces were continued; and the most unscrupulous measures were, on the other hand, exercised against them. In 1599, the lord-lieutenant entered the county with a force of 2500 men, and totally defeated the O'Conors; but in the following year they became as troublesome as before; until at length Sir Oliver Lambert was sent thither at the head of 1000 foot and 100 horse, and after raising the siege of Philipstown, which had been closely pressed by the insurgents, he dispersed them so completely that no resistance of any importance was afterwards attempted.
Transcribed from A Topographical Dictionary of Ireland, 1840 by Samuel Lewis