The modern town grew up as a settlement around the de Barry castle in the 12th century and was later the site of an English garrison. A military barracks operates in the town to this day. Armed conflict has been the centrepiece of the town's historical heritage. French forces under the command of General Humbert aided in a rout of the English garrison in the town during the failed Irish Rebellion of 1798. This was so comprehensive that it would be known as "The Races of Castlebar". A shortlived provisional Republic of Connaught was declared following the victory and John Moore, head of the Mayo United Irishmen and the brother of a local landowner, was declared its president. His remains are today interred in a corner of the town green, known as the Mall, previously the cricket grounds of Lord Lucan, whose family, the Binghams, have owned and own large tracts of the town and county. The town received its charter from King James I in 1613 and is today governed by an urban district council, a subdivision of Mayo County Council. The Lake in Castlebar is also known as Lough Lannagh.
The Irish National Land League was founded by Michael Davitt, of Straide in Co. Mayo, at the Imperial Hotel in Castlebar on 21 October 1879.
Castlebar is home to The Linenhall Arts Centre which exhibits visual art throughout the year, as well as hosting live drama and music performances. The Linenhall also organises a children's arts festival (Roola Boola) annually. The Royal Theatre, with a capacity of two thousand, hosts larger-scale productions and popular music concerts.
There are Roman Catholic, Church of Ireland (Anglican, Elim Pentecostal and Spiritualist churches in the town. There is a recently established Mayo male voice choir, and Mayo Orchestra. Throughout the 1980s and 1990s, Castlebar experienced significant immigration, growth and investment.
Castlebar is the second biggest retail centre in Connacht, after Galway city. A survey by consultants Experian showed that e284 million is spent in by shoppers in Castlebar every year. The Irish Retail Centre Rankings (http://press.experian.com/documents/showdoc.cfm?doc=3152) show Castlebar is the 12th biggest retail centre in the Republic of Ireland in terms of retail spend, and 20th on the island of Ireland overall.
However, the survey counts many major shopping centres separately from the cities they are situated in. If the spend for several major shopping centres in the Dublin area are included with the Dublin figures, Castlebar moves up to the seventh-biggest retail centre in the Republic. It is surpassed only by the Republic's five main cities, and the town of Tralee.
The local soccer team is Castlebar Celtic. They currently have a team playing in the Mayo Super League. In addition to this they have a thriving underage structure in place. They compete in the Ulster/Connacht section of the Eircom U-21 League of Ireland. They play their home games in Celtic Park. Other local soccer teams include Snugboro United who have their home at Conway Park just on the outskirts of the town and the junior soccer team, Ballyvary Blue Bombers.
There is a Rugby Union club, with pitch and clubrooms near the town, with active participation in provincial and national leagues.
There is an 18 hole golf club in the town, as well as active basketball and other clubs. The council provides an indoor heated swimming pool and there are numerous gyms.
The Web Site for the region can be found at www.castlebar.ie
As of 3rd June 2008 the Web site is shut down due to a threat of legal action by Tony Geraghty, editor of the local free paper Mayo Echo following comments posted (and subsequently removed at Mr Geraghty's request) following a controversial article printed in the paper.
Since publication of the original article, the debate has moved onto national radio, and groups have been formed on Facebook and Myspace in support of the Web site. There is also a campaign site with a link to a petition.