The area covered by the present parish of Ballycastle is roughly that known as 'The Lagan' in the old Irish records. The Lagan comprised the valley or hollow tract of land, which is surrounded on the East by the Hill of Kilbride, on the South by Athleague Hill, then to a range of hills as far as Ballinglen, to the sea which formed its northern boundary. From its natural appearance, the area got the name of 'The Lagan' or 'Little Hollow'

The older parishes of Doonfeeney & Kilbride amalgamated in 1804 to form the present day parish of Ballycastle. Until then, Ballycastle was just a townland in the parish of Doonfeeney. The name Ballycastle was in use by about 1470.

From Staffords survey, we know that the town was founded in 1797 on the property of John Knox Esq. of Castlereagh. Thomas Palmer Esq. Summerhill, held it on lease and sublet the ground to the inhabitants of Ballycastle by leases of one life at 40 shillings per acre. The town consisted of 82 houses built of stone. The Church of Ireland was built in 1827 and the Catholic Church in 1828. The present day Church, St. Brigid's, was built in 1931.

Lewis Topographical Dictionary (1837), tells us that many new houses had been built; that a market place was in the course of construction; that a new line of road was being built to Belmullet; that there were petty sessions every Wednesday; that it was a constabulary and chief revenue-Police Station and had six fairs in the year and a penny post to Killala. There was also a Coastguard Station over the present day pier.

During the famine Ballycastle suffered very badly. Sixty seven people died in Ballycastle. At this time, St. John's Hall was built as a soup kitchen.

In 1881, a Model Farm was established by the Edinburgh Ladies Society. It was run by the Presbyterian Church and consisted of about 230 acres. Its main aim was to educate boys in better farming techniques and girls in domestic crafts.

Ballycastle, because of its situation on the coast, formed a natural travel route from Ballina to Belmullet. Access to Crossmolina was afforded up the Glen Road. This led to the establishment of a market town. However, widespread use of the motor car and the opening of the mart in Ballina in the 1950's caused Ballycastle to decline. To reflect the fall in population, Kilbride school closed in 1956, Glenurla school in 1965 and Killeen school in 1969. The remaining pupils from the three schools were provided with a school bus to Ballycastle.

In the 1970's, the area was being promoted as a tourist attraction. Ballycastle celebrated its Bicentennial in 1997. On 10th August, President Mary Robinson officially opened the Centre of the Ballinglen Arts Foundation. She also closed the 10 day festival and planted a yew tree in the church grounds.

1974: The holiday cottages were built.

1979: A new Health Centre was built and a new premises for the Fire Brigade. The landmark thatch cottage belonging to Tommy Loughney at the junction of Main Street and the Glen Road was demolished for road widening.

1985: The first 24 houses in Seaview Estate were built by Mayo County Council.

1992: A new National School was built and the Céide Fields Centre opened.

1995: Ballycastle/Belderrig Development Co. Ltd was set up.

1996: Four more houses were added in Seaview Estate.

1998: Great improvements take place in the town such as: replacement of water mains, installation of sewage piping, ESB cables laid underground and provision of new street lighting.

1999: Eight more houses built in Seaview Estate and The Resource Centre was opened.

2000: Stella Maris Secondary School/Convent closed in June 2000 and the remaining Mercy Nuns left Ballycastle.