Claremorris, or in Irish 'Clar Cloinne Mhuiris" (the plain of the family of Maurice) takes its name from the famous Norman invader, Maurice de Prendergast who came to Ireland with Strongbow in 1170 and who was later granted a large portion of lands in these parts. Local tradition believed that his son, Gerald, or one of his decendents, who had built the 13th century Brize castle, near Balla, as the family residence, caused the growth of Claremorris town by building a "clar" or bridge over the river linking Mayfield and Clare Loughs, but this is very doubtful.
Although Claremorris as a town appears not to have existed earlier than 300 years ago its surrounding countryside was well inhabited for centuries earlier. The remains of ring forts dotting the landscape pin-point sites of human habitations, some of which date back over 1000 years. Ballinasmalla Abbey was founded in 1288 by the Prendergast family and was once a very extensive building having is own mill-race. It was occupied by Carmelite priests who said Mass there until about 1875. Mass is still celebrated annually at the Abbey. The parish church at the time was Kilcolman Church near Barnycarroll.
The fact that most of the resident landlords of this region had built their mansions close to Claremorris during the 1600's suggest fairly widespread habitation in this area as well as a clear reason for the origin of the town.
Castlemagarrett, later the seat of Lord Oranmore and Browne, was built in 1864 by Geoffrey Browne as his home shortly after his marrage to Mary, daughter of Danel Prendergast, the previous owner of the estate. Daniel Prendergast was a descendant of the Prendergasts of Brize Castle, Balla. The Brownes had held property in these parts for over 500 years before this marriage.
The Lamberts of Brookhill, who came here in 1690 originally came to Connaught with Cromwell around 1650. The Kelly's (former owners of what is now St. Colman's College) came to Castlegar shortly after 1665, as did the Kirwans of Claremount. Over the next 250 years most of the native Irish eked a meagre existance as tenants or servants of these landlords.
It was probably during the late 1600's or early 1700's that Claremorris town began to evolve. Although Claremorris was not originally on any principal road or trade route it is likely that a charter of old fairs was granted in the early 1600's.
By 1777 the basic linear pattern of the town with its distinctive market square had developed. In 1802 Claremorris, McParland claims, was "the only real town in the barony....the dwelling houses were built of stone, with chimneys and mostly separate outhouses. It also had a 3 day-a-week postal service. In 1822 the R.C.Chapel was built, this was later demolished and the site now houses the town hall. The present Roman Catholic Church was built in 1911. Also at this time a large Courthouse was built, as was St. John's Protestant Church and Schools which were opened in 1828. St. Johns's Church is now the town library.
By 1836 Claremorris had about 300 houses, principally slated, 1476 inhabitants, a Wesleyan Methodist Meeting house, the chief station of the constabulary and revenue police, 12 privately run schools and a brewery.
During the early 1800's Claremorris was tightly controlled by the notorious and much feared P.C. and High Sheriff for Mayo, Denis Browne, M.P., (1763-1828) - no relation to the Castlemacgarrett Brownes - who was the resident magistrate and local landlord living at Claremount House.
Between 1820 and 1880 Claremorris and its neighourbood endured the ravages of famine on a number of occasions. In 1851 the Workhouse was opened as a last refuge for the local destitute families until it closed in October 1918. 1863 saw the coming of the railways to the town. It was at Nally's Hotel in James Street (now the A.I.B. bank) that the now famous Land League Meeting at Irishtown in 1879 was originally planned.
Over the last century, Ireland's history has being influenced by Claremorris men and women.
Claremorris was the birthplace of Connaught GAA and the first Connaught Council meeting took place here in 1902. The Land League flag was made here and was carried the 7 miles to Irishtown in 1879 for the foundation of the Land League by Michael Davitt. A Famine Workhouse opened in Claremorris in 1841.