"CASTLE-ISLAND, a town and parish, in the barony of TRUGHENACKMY, county of KERRY, and province of MUNSTER, 8 miles (S.E. by E.) from Tralee; containing 6161 inhabitants, of which number, 1570 are in the town. This place derives its name from the "Castle of the Island of Kerry", erected by Geoffrey de Marisco in 1226, and which, in 1345, was taken by Sir Ralph Ufford, lord-justiciary of Ireland from Sir Eustace de la Poer and other knights, who held it for the Earl of Desmond, and on being captured were immediately executed.
The town is situated on the river Maine, and at the junction of the mail coach roads from Tralee and Killarney to Limerick; and on the completion of the new Government road from King-William's-town, it will be also on the direct road from Tralee to Cork. It consists chiefly of one long street extending nearly east and west, with a market-house at the western extremity, from which the road to Tralee branches off on the north-west; it had formerly a market and a daily post. The new Government road has opened a line for a new street, which will diverge at right angles from the south side of the main street towards King-William's-town.
This was once the capital of the county, and the assizes were formerly held here; but since Tralee became the county town, the place has declined very much, and its market has been discontinued.
The parish comprises 32,577 statute acres, as aplotted under the tithe act; the soil is various. Part of it is within the seigniory of Castle-island which belongs to Lord Headley, and consequently participates in the extensive and beneficial improvements in 1823 in this previously barren and unprofitable district. Among these are branch roads constructed at his expense from the new Government road between Castle-island and Abfeale, extending nearly 10 miles, and affording a facility of communication with every farm. "
[From A Topographical Dictionary of Ireland by Samuel Lewis (1837)]
"About eight miles to the east of tralee stands Castle Island, formerly called the Castle of the Island of Kerry. This castle is said to have been erected by Geffry Maurice, or de Mauriscis, Lord Justice of Ireland, in 1226, during the reign of King Henry III, the ruins of which castle are still remaining. Round the walls the River Mang, being put here but an inconsiderable stream, flowed in a kind of ditch, over which were formerly draw-bridges, portcullices, etc.
In Castle Island are a decent parish church, a good parsonage house, a foot barrack, a session and market house, with a handsome assembly room for dancing.
This town being well warered, and fuel very cheap, is a proper place for linen and other manufactures, who by settling therein, may be assured of meeting with all due encouragement."
[From The Ancient and Present State of the County of Kerry by Charles Smith (1756)]