The O’Reilly clan (still a very common surname in the area) established a castle in the town in the late 13th century. A Franciscan monastery was also established at around the same time. In the 15th century the local ruler, Bearded Owen O’Reilly set up a market which attracted merchants from Dublin and Drogheda. The term life of Reilly was credited to the O’Reilly clans due to their great wealth and power, having issued their own currency during the 17th century. King James I granted the town a charter in 1610. Later during the 17th century local administrative influence and power passed to the Maxwell family, descendants of Robert Maxwell, Bishop of Kilmore (1643-72), who later became titled Lords Farnham.
Development in Cavan during the early 19th century saw the building of a new wide street that still bears the name Farnham Street. Away from the markets area of the town, Farnham Street was lined with comfortable town houses, public buildings (such as the courthouse which dates from 1825) and churches. From the mid 19th century, Cavan became an important rail junction for the Midland Great Western Railway (MGWR) and those of the Great Northern Railway (GNR). The Town Hall was built in 1909. In 1938, work began on the Roman Catholic Cathedral of Saints Patrick and Felim. Five kilometres (3 mi) west of Cavan Town is the Church of Ireland Kilmore Cathedral, which contains a Romanesque doorway dating from the 12th century reputed originally to have come from Trinity Abbey, located a short distance away upon an island in Lough Oughter. Farnham House, to the northwest of Cavan, is one of the largest houses in the county. It is believed to have been built for the Maxwell family, holders of the title of Baron Farnham, in 1810, and to have been designed by Francis Johnston, a County Armagh-born, but Dublin-based, architect. It was recently sold by Diana, Lady Farnham (widow of Barry Owen Somerset Maxwell, 12th Lord Farnham) to a local entrepreneur, and the house and estate has now been converted to a luxury hotel and leisure complex under the Radisson SAS international hotel group. On 23 February 1943, a fire at St Joseph’s Orphanage in the town claimed the lives of 35 children and an elderly woman. A Public Enquiry found no culpability on the part of the nuns who ran the orphanage, but the circumstances surrounding the high death toll in the fire remain controversial to this day.
In ancient times Leitrim formed the western half of the Kingdom of Breifne. This region was long influenced by the O’Rourke family of Dromahair, whose heraldic lion occupies the official county shield to this day. Close ties initially existed with East Breifne, now County Cavan, and the O’Reilly clan seated there. The Normans invaded in the 13th century and occupied the south of Breifne. Much of the county was confiscated from its owners in 1620 and given to Villiers and Hamilton. Their initial objective was to plant the county with English settlers. However, this proved unsuccessful. English Deputy Sir John Perrot had ordered the legal establishment of “Leitrim County” a half-century prior, in 1565. Perrott also demarked the current county borders around 1583. Five forests are traditionally said to have stood in Leitrim up till the 17th century.
Leitrim was first hit by the recession caused by the mechanisation of [linen] weaving in the 1830s and its 155,000 residents (as of the 1841 census) were ravaged by the Great Famine and the population dropped to 112,000 by 1851. The population subsequently continued to decrease due to emigration. After many years, the wounds of such rapid population decline have finally started to heal. Agriculture improved over the last century. Leitrim now has the fastest growing population in Connacht.
Working of the county’s rich deposits of iron ore began in the 15th century and continued until the mid 18th century. Coal mining became prominent in the 19th century to the east of Lough Allen in Sliabh an Iariann and also to the west in Arigna, on the Roscommon border. The last coal mine closed in July 1990 and there is now a visitor centre. Sandstone was also quarried in the Glenfarne region. William Butler Yeats spent the turn of the twentieth century fascinated with Lough Allen and much of Leitrim. In the northwest, 11 km from Manorhamilton can be found Glencar Waterfall, which was an inspiration to Yeats and is mentioned in his poem The Stolen Child.