"COUNTY MAYO, a maritime county of the province of Connaught, Ireland. It is situated in the N.W. part of the island, and is bounded by the counties of Sligo and Roscommon on the E., the ocean on the N. and W., and county Galway on the S. It lies between 53° 28' to 54° 21' N. lat., and 8° 25' to 10° 5' W. long., and extends over an area of 2,131 square miles, or 1,363,882 statute acres, of which 497,687 are arable, 56,976 are under water, 8,360 in plantation, 800,111 uncultivated, and 848 are occupied by the sites of towns, roads, &c. Its length from N. to S. is 58 miles, and its extreme breadth from E. to W. is 72 miles. The coast is rugged and forbidding, but is broken by numerous indentations, the principal of which are, the Bay of Killala, with its extensive fisheries, Broadhaven, Blacksod, Tulloghane Bay, Clew Bay, an expanse of water with numerous islands, Bullan Bay, Westport, &c. The principal promontories of the coast are, Belmullet, Benwee Head, with the Stag's rocks, Eagle island, with its lighthouse, Erris Head, Mullet peninsula, Achill Head, with its lofty cliffs, Achillbeg, Clare island, with lighthouse, Innisgort, with light, Runa Head, Innisturk, Bofin Bank, where cod are taken, the Killeries, and Inistegil. The surface of the county is very various, comprising a large proportion of bog, alternated with fertile soil, mountainous and lake districts. The principal summits are, Mulrea, 2,683 feet; Benbery, 2,610; Croaghpatrick, 2,510; Bengorm, 2,224; Fermnamne, 2,210; Bengorriff, 2,038; Slieve Bohaim, 1,294, rising S. of Clew Bay, in the S.W. of the county; Achill Head, 2,222; Slieve More, 2,217; Slieve Cor, 2,368, Curraun Achill, 1,786; Nephin Beg, 2,012; Cushcamcurragh, 2,262; Nephin, 2,64¾; Buckoogh, 1,922; Bereen Curragh, 2,295; Slieve Turk, 1,322, rising to the N. of Clew Bay. The Croagh Moyle mountains are in the interior. Slieve Gamph, 1,321 feet, rises towards the E.; Knocklettercass, 1,208 feet; Maumakeogn, 1,243; Slieve Fyough, 1,090, in the N. The principal lakes are, loughs Corrib and Mask, Conn and Cullin, Carra, Beltra, Carrowmore, Lavalla, Feagh, and Furnace. There are numerous other lakes of less importance within the limits of the county. The chief rivers of Mayo are, the Moy, navigable to within a short distance of Ballina, and the only navigable stream of the county; the Owen, Oweninny, Owenmore, Deel, Robe, Ayle (partly subterranean), Amoy, Trimogne, and Shaddagh, with numerous other small streams, chiefly tributary to these.
The climate of the county, owing to its extensive line of sea-coast, is damp, and subject to frequent rains and humid fogs, but is not considered unhealthy. The geological formations of the county consist chiefly of red sandstone, an extensive belt of which stretches between the N. side of Clew Bay and Lough Conn, and round Beltra, mica slate, granite, and quartz. The mica slate and quartz occur nearly all through the mountains of the W. To the N. of Lough Conn, and away to the river Oweninny, the surface consists of mountain limestone, and limestone forms the principal subsoil in the level districts. Several valuable marble and slate quarries are worked. Iron ore exists to some extent, but is not worked. Manganese, and potters' clay are found in abundance. There are indications of coal at Slieve Garnon. The inhabitants of the county are chiefly employed in agriculture and in the fisheries. The salmon fishery of the Moy and other streams is an important branch of industry, and on the coast ling, sole, turbot, herring, cod, oysters, lobsters, and seals, are taken. Greater attention is paid to pasturage and the rearing of cattle than to agriculture, which is in a backward state. The arable soils are mostly fertile, and much enriched by plentiful manurings of sea-weed. The cotton trade has greatly declined of late years, but there are still some manufacturers, chiefly at Ballyclare, who produce goods for domestic use. The fences of the country are constructed of stone or turf. Owing to the scarcity of wood, the peasants occupy huts of a wretched description. The farm labourer is paid at the rate of about 8d. a day, without rations of any kind. This county is divided into nine baronies, viz: Burrishoole, in the W.; Carra, in the midst; Clanmorris, in the S.E.; Costello, in the E.; Erris and Tirawley, in the N. and N.W.; Gallen, in the N. E.; Kilmaine, in the S.; and Murrisk, in the S.W. These baronies include 73 parishes. The principal towns are, Castlebar, the county town, Westport, Ballinrobe, Ballina, Ballaghadirreen, Swinford, Claremorris, Crossmolina, Newport, Killala, and Foxford. The first four, with Swinford, are Poor-law Unions. The assizes are held at Castlebar, and quarter sessions are held at six of the above-named towns. This county is within the military district of Dublin, and has barracks at Castlebar, Ballinrobe, Westport, Foxford, and Ballaghadirreen. Along the coast there are 22 coastguard stations, and 455 police stations in the county. It is in the Connaught circuit, and the dioceses of Tuam, Killala, and Achonry. Mayo returned four members before the Union to the Irish parliament, and now returns two to the imperial parliament. Constituency in 1859, 3,779. The population of the county in 1851 was 274,830; in 1861, 254,796. It is governed by a custos rotulorum, lieutenant, high sheriff, 27 deputy lieutenants, magistrates, &c. Mayo was the ancient territory of the Magnatæ. It appears to have been constituted a county in the time of Edward III. It was granted to the family of De Burgho by Henry II., who revolted in 1333, when William de Burgho, Earl of Ulster, was assassinated; and various parts of the county have at subsequent periods, especially during the troubled times of 1641, been the scene of rebellion and conflict, which will be more appropriately noticed under the names of the various localities in which they transpired. The principal objects of antiquity to be found in Mayo are, round towers at Killala, Mellick, Aughnagower, Balla, and Turlough; Druidical stones at Westport; abbey ruins at Burrishoole, Ballyhaunis, Ballintubber, Moyne, Rosserk, and Ballysakeery; castle ruins at Doona, Dunbriste, Ballylahen, Ballinglen, Deel, Castle Island, Portnakally, Shrule, Carrig, a Hooly, and Clare island. The last are Grace O'Malley's. The chief communications of the county are the Athlone and Castlebar section of the Great Northern and Western railway, and the coach roads, from Castlebar to Minola, Kilcolman, Ballyhaunis, Castlerea, Roscommon, and Dublin; to Lough Conn, Foxford, Ballina, Killala, and Sligo; to Lough Beltra in Glenhest, Owen Inny river, Bangor, Belmullet, and Erris Head; to Newport and Clew Bay, Bunown, Curran, Achill, and Achill Head to Clonkeen, Westport, Croaghpatrick, Killeries, and Clifden; and lastly to Balcarra, Burriscarra Abbey, Ballinrobe Cross, Rossduff; and Galway. The principal seats in the county are. Castlebar, of Earl Lucan; Westport, of the Marquis of Sligo; Newport, of Lord Clanmorris; Loughglyn, of Viscount Dillon; Neale, of Lord Kilmaine; Castlemacgarrett, of Lord Oranmore; Newport, of O'Donnell, Bart.; Kilboyne, of O'Malley; and Athvallie, of Blosse, Bart., &c."