‘Maynooth Castle was the original residence of the Kildare family. The manor of Maynooth in 1176 was granted by Strongbow to Maurice Fitz-Gerald, who erected the castle for protection against the incursions of the natives. His son Gerald, first Baron of Offaly, obtained from John, Lord of Ireland, son of Henry II, a new grant of sundry lordships. Thomas, second Earl, was married to a daughter of the Red Earl of Ulster, and sister to Ellen, the wife of Robert Bruce, King of Scotland. During the latter half of the fourteenth century, Maynooth was one of the border fortresses of the Pale, or English possessions, in the defence of which Maurice, fourth Earl of Kildare, distinguished himself. John, the sixth Earl, enlarged the castle (1426) and it was then said to be “the largest and richest earl’s house in Ireland”.’
From an article on Carton in The Journal of Horticulture and Cottage Gardener, Vol.22, May 16, 1872. 

‘In March 1535 the new Earl of Kildare had with him 120 horse, 240 gallowglasses and 500 kerns. Leaving Maynooth Castle strongly fortified in the hands of his foster brother and confidante Christopher Pareses, he went into Offaly to raise additional adherents for the summer campaign. Skeffington [Sir William Skeffington, then Lord Deputy of Ireland] invested Maynooth Castle of the 14th March, and on the 23rd Parese, consenting to betray his trust, permitted the outer defences to be taken without resistance, after which the keep was carried by assault. A park of heavy artillery, brought up to the siege by the English, and for which the Anglo-Irish were quite unprepared, had no small effect in compelling such a speedy surrender of a place the Earl of Kildare regarded as almost impregnable. Of the garrison, twenty-five were beheaded and one hanged, as it was thought dangerous to spare skilled soldiers. “Great and rich was the spoile, such store of beddes, so many goodly hangings, so rich a wardrobe, such brave furniture, as truly it was accounted, for household stuffe and utensils, one of the richest earl his houses under the crown of England.” Pareses, to increase the estimation in which his treachery should be regarded, dwelt on the trust and confidence bestowed on him; and Stanihurst tells us how his treachery was rewarded; “The Deputy gave his officers to deliver Parese the sum of money that was promised, and after to choppe off his head”.’
From an account of the Rebellion of Silken Thomas and the Siege of Maynooth given in A Compendium of Irish Biography by Alfred Webb, Dublin, 1878.

‘On the 7th January, 1642 a party of Catholics seized and pillaged Maynooth Castle, carrying off the furniture and the library, which was of great value; all the stock, including thirty-nine English cows and oxen, thirty horses worth £270, household goods worth at least £200, and corn and hay worth £300; they also deprived him of rents amounting to at least £600 a year. The castle was soon retaken, but in 1646 was occupied by a detachment sent for that purpose by the Catholic general, Preston [Thomas Preston, first Viscount Tara], when he was advancing against Dublin, and on his retreat it was dismantled, and has never since been inhabited.’
From The Earls of Kildare and Their Ancestors from 1057 to 1773 by the Marquis of Kildare (future fourth Duke of Leinster), Dublin, 1858.