CASTLETOWN-DELVIN, a market and post-town, and a parish, in the barony of DELVIN, county of WESTMEATH, and province of LEINSTER, 10 miles (N.E. by E.) from Mullingar, and 39- (N. N. W.) from Dublin ; containing 4513 inhabitants, of which number, 419 are in the town. The castle was built by Hugh de Lacy, Lord of Meath, for his brother-in-law, Sir Gilbert de Nugent, who resided in it for some time, and then built the neighbouring castle of Clonyn, which was burnt at Cromwell's approach during the parliamentary war. The town contains 77 houses : the market is on Friday, and fairs are held on the 17th of March and 1st of May and December, for cattle. Petty sessions are held every alternate Monday, and here is a station of the constabulary police, The parish is situated on the road from Athboy to Drumeree, and contains 15,659 statute acres, as applotted under the tithe act, besides a considerable quantity of waste land. There are tracts of bog and small lakes ; and limestone is abundant, but is not worked. The land which is generally good, is principally under tillage and pasture. Clonyn, the residence of the Marquess of Westmeath, a descendant of Sir Gilbert de Nugent, is close to the town, and is surrounded by extensive grounds richly ornamented with timber. The other seats are South Hill, the residence of W. Chapman, Esq. ; Mitchelstown, of G. Hinds, Esq. ; Rossmead, of H. W. Wood, Esq., surrounded by fine plantations ; Ballyhealy, of P. Batty, Esq. ; Clonmaskill, of Laurence Loyd Henry, Esq. ; and Areherstown, the property of R. Smyth, Esq. The living is a vicarage, in the diocese of Meath ; the rectory is partly impropriate in Nicholas Ogle, Esq., and partly appropriate to the vicarage, which was united by diocesan authority, in 1821, to the entire rectory of Clonarney or Clonarvey, and is in the patronage of the Crown and the Marquess of Drogheda, The tithes amount to £449. 18., of which £276. 18. 5. is payable to the impropriator and the remainder to the vicar ; and the gross tithes of the benefice amount to £258. 9. 2-. The church is a plain building of ancient date, but in excellent repair. The glebe-house was built in 1815, by aid of a gift of £400, and a loan of £320, from the late Board of First Fruits : the glebe consists of 13- acres of land valued at £18. 9. 2. per annum. In the R. C. divisions the parish forms the head of a union or district, comprising also the parishes of Kihweilagh and Killagh, and containing two chapels, one at Castletown-Delvin, the other at Killulagh. There is a school at Ballyhealy under the patronage of Mrs. Batty, and one at Moor-town supported by the Marquess of Westmeath ; there is also a national school at Ballinvalley. In these schools are 96 boys and 121 girls ; and 170 boys and 110 girls are educated in five private schools. A dispensary is supported in the usual way. The ruins of the old castle built by De Lacy occupy the sides of a quadrangle, with a round tower at each corner ; and on eminences near Archerstown are the ruins of two ancient castles, and on a hill further west stands a very conspicuous tower. There is also a round tower on a hill to the south-west of the town and another near Ballyleahy. The remains of a large fortress occupy the summit of an abrupt eminence on the eastern side of the parish ; and there are remains of other strong buildings at Cullydougran, on the opposite border. The Marquess of Westmeath enjoys the inferior title of Baron Delvin, in the peerage of Ireland.