ROSCOMMON, an inland co. of Ireland, in the e. of the province of Connaught, and bounded on the e. by the river Shannon, is 60 rn. long from n. to s., by 40 m. from e. to west. Area, 607,691 acres, of which 440,522 are arable. Pop. '71, 140,670. 737 per sons speak Irish only. Number of pupils on the roll of the national schools in Dec.,. 1875, 32,654 (of whom 32,186 were Roman Catholics). Numbersof emigrants from Ros common between 1851 and 1871, 52,299. The surface of Roscommon, which belongs to the central plains of Ireland, is level, with undulations rising in the s. into the Slieve Bawn range, the highest point of which is 867 ft. in height; and on the n., into the Cur lew mountains, of which Slieve Curkagh attains a height of 1098 feet. Its principal rivers are the Shannon (q.v.) and the Suck. Roscommon communicates by means of the Midland Great Western, and the Southern and Western, and Northwestern railways, with all the extremities of the kingdom. In geological structure it belongs to the central limestone formation, in some districts of which the sandstone protrudes. The soil in the central district is in general light, but fertile, and affords the finest sheep-pasture in Ire land—the celebrated "plain of Boyle." Some portions also contain a rich and fertile
loam, which produces good cereal crops; but the chief industry of the Roscommon farming population is the feeding of sheep and cattle, especially the former.—The county can hardly be said to possess any manufacture worthy of mention. The chief towns are Roscommon (q.v.), Boyle, Castlerea, Flphin, Strokestown. Ballinasloe and Athlone lie upon the border, and are partly within this county. Roscommon, in the ante-English period, was the country of the septs of MacDerrin3t, O'Daly, O'Kelly, and above all, O'Conor, of which there were two branches, that of the ()Vapor Roe (red), and that of O'Conor Don or Dhun (brown). The present representative of the O'Conors, the O'Conor Don, is one of the very few Irish princes who have succeeded to the heredi tary estates of their ancestors.
Roscommon sends two members to the imperial parliment, It possesses a vast num ber of antiquities of the Celtic period, raths, etc.; a portion of a round tower at Oran, several remains of strong castles of the English period, and some fine ecclesiastical ruins, of which Boyle, Roscommon, Tulsk, and Clonshauville are the principal.