The town has, at either end of the main street, Maynooth Castle and Carton House: two former seats of the Dukes of Leinster. The castle was a stronghold of the 16th century historical figure Thomas FitzGerald, 10th Earl of Kildare better known as Silken Thomas. The castle was overrun in 1535, after the rebellion of the Earl. The town is just inside the western edge of The Pale.

The most important historical buildings in the town are those of St. Patrick's College and some of which antedate the foundation of the college, while others are in the late Georgian and neo-Gothic revival style. The "new range" of buildings was erected by A.W.N. Pugin in 1850 under a commission from then college president Laurence F. Renehan, while the highly important College Chapel was designed and completed by J.J. McCarthy during the presidency of Dr. Robert Browne in 1894.

In the 1920s, the town was the unofficial home to the King of England's representative in Ireland, Domhnall Ua Buachalla, who declined to take up official residence in the Viceregal Lodge in the Phoenix Park, and whose family operated a hardware store in the town until 2005, the only store with an Irish language name in the town for many years.