A temple of Heracles Monoecus was built on the Monaco headland at a very early date, probably by the Greeks of Massilia. Monoeci Portus or Portus Herculis is frequently mentioned by the later Latin writers. From the 10th century the place was associated with the Grimaldi, a powerful Genoese family who held high offices under the republic and the emperors; but not till a much later date did it become their permanent possession and residence. In the beginning of the 14th century it was notorious for its piracies. Charles I. (a man of considerable mark, who, after doing great service by sea and land to Philip of Valois in his English wars, was severely wounded at Crecy) purchased Mentone and Roccabruna, and bought up the claims of the Spinola to Monaco. The princes of Monaco continued true to France till 1524, when Augustin Grimaldi threw in his lot with Charles V. Honoré I., Augustin’s successor, was made marquis of Campagna and count of Canosa, and people as well as rulers were accorded various important privileges. The right to exact toll from vessels passing the port continued to be exercised till the close of the 18th century. Honoré II., who renewed the alliance with France in 1641, was compensated for the loss of Canosa, &c., with the duchy and peerage of Valentinois and various lesser lordships; and duke of Valentinois long continued to be the title of the heir-apparent of the principality. The National Convention annexed the principality to France in 1793; restored to the Goyon Grimaldis by the Treaty of Paris in 1814, it was placed by that of Vienna under the protection of Sardinia. King Albert of Sardinia took the opportunity of disturbances that occurred in 1848 to annex Mentone and Roccabruna; but this high-handed proceeding was condemned by the protocol of 1856, and Charles III. (born 1818) entered upon his full rights. With the transference of Nice to France in 1860 the principality passed again under French protection.

See Charles de Venasques, Genealogica et historica Grimaldiee gentis arl·or (really the work of Honoré II.).

Climate and Agriculture. — Partly owing to the large proportion of bog and water the climate is somewhat moist. The soil in the more level portions of the county is very fertile where it rests on limestone, and there is also a mixed soil of deep clay, which is capable of high cultivation; but in the hilly regions a strong retentive clay prevails, which could be made productive only by careful draining and culture. Spade husbandry generally prevails. The most common manure is a compost of lime and burned turf mould. Marl is abundant, but is little used, and gypsum also is found.

The number of holdings in 1881 was 17,849, of which as many as 10,784 did not exceed 15 acres in extent, and 2870 of these did not exceed 5 acres; 6454 ranged between 15 and 50 acres, and only 24 were above 200 acres. The area of arable land was 278,755 acres, or 87 per cent, of the whole, while 5258 were under plantations, 7580 bog and marsh, 5239 barren mountain land, and 21,582 water, roads, and fences. The following table shows the areas under the different crops in 1850 and 1882 :— [table]

Horses numbered 10,229 in 1872, and 10,666 in 1882. In the same years mules numbered 300 and 469, and asses 4314 and 3476. The number of cattle in 1872 was 81,333, and in 1882 only 72,266, an average of 25’9 to every 100 acres under cultivation, the average for Ireland being 25’8. Sheep between 1872 and 1882 declined from 17,964 to 9858, a very inconsiderable number; pigs increased from 26,008 to 29,972; goats from 8873 to 12,391; and poultry from 341,874 to 434,260.

According to the latest return, the land was divided among 1470 proprietors,who possessed 311,440 acres,with a total annual value of £261,382. The average size of the properties was 211 acres, and the average value per statute acre 17 shillings. The following seven proprietors possessed upwards of 10,000 acres: E. P. Shirley, 26,386; marquis of Bath, 22,762; earl of Dartrey, 17,345; Lord Rossmore, 14,839; Sir John Leslie, 13,621; Viscount Templetown, 12,845; A. A. Hope, 11,700.

Manufactures.— The only manufacture of consequence is linen, which of late years has been on the increase. The number of scutching mills in 1881 was 55, of which 45 were wrought by water, 8 by steam, and 2 by water and steam.

Administration.— The county includes 5 baronies, 23 parishes, and 1850 town lands. Assizes are held at Monaghan, and quartersessions at Carrickmacross, Castleblayney, Clones, and Monaghan. There are 8 petty sessional districts within the county, and part of another. It includes the poor-law unions of Carrickmacross and Monaghan, and portions of Castleblayney, Clogher, Clones, Cootehill, and Dundalk. It is in the Belfast military district, subdistrict of Armagh. There is a barrack station at Monaghan. In the Irish parliament two members were returned for the county and two for the town of Monaghan, but at the Union Monaghan was disfranchised.

Population.— The population in 1841 was 200,442; but in 1851 it had diminished to 141,823, in 1871 to 114,969, and in 1881 to 102,748, of whom 50,077 were males and 52,671 females. At the last census 73 per cent, of the inhabitants were Roman Catholics, 13 per cent. Episcopalians, and 11 per cent. Presbyterians. The number of emigrants from 1st May 1851 to 31st December 1881 was 56,408, or about 1840 persons per annum; while during the twenty years ending 31st March 1881 the annual rate of emigration was 13 '8 per 1000 of the population. The death-rate to every thousand of the population for the ten years ending 1881 was 16 9, the birthrate 23 - 4, and the marriage-rate 3'6. The towns possessing more than 1000 inhabitants are—Monaghan 3369, Clones 2216, Carrickmacross 2002, Castleblayney 1810, and Ballyblay 1654. Monaghan, the county town, received its name Muinechan (the town of monks) from a monastery founded there at a very early period. The town was incorporated by James I., but it was little more than a hamlet till towards the close of last century. Besides the usual county buildings, it contains a Roman Catholic college, and National model schools.

History and Antiquities.— In the time of Ptolemy, Monaghan formed part of the territory of the Scoti. Subsequently included in the district of Oriel or Orgial, and long known as Macmahon’s country, it became shire ground in the reign of Elizabeth.

The antiquarian remains of Monaghan are comparatively unimportant. At Clones there is a round tower in good preservation, but very rude in its masonry; another at Inniskeen is very dilapidated. Near Clones there are two large raths. Although there are several old Danish forts, there are no mediaeval castles of importance. The only monastic structure of which any vestiges remain is the abbey of Clones, which was also the seat of a bishopric. The abbey dates from the 6th century, but was rebuilt in the 14th century after destruction by fire. On the site of the Franciscan abbey at Monaghan a castle was erected, which was in a ruinous condition in the time of James I.