Originally one of the Gaelic 'countries'129 escheated (along with Armagh, Tyrone, Londonderry, Cavan and Fermanagh) following the Flight of the Earls in 1607, Donegal was part of the Plantation of Ulster. As a county it developed late and within the framework of the plantation, which encouraged English and Scottish settlers to take up land grants and settle them with their followers. All the five boroughs - Ballyshannon, Donegal, Killybegs, Lifford and St Johnstown - were incorporated between 1611 and 1616 in the expectation of future development, and all were disfranchised by the Act of Union in 1800. Apart from the Finn and Foyle river valleys much of the country was mountainous and infertile. At the beginning of the century Lord Abercorn and the Gores were allied and probably joined by the Conolly-Conyngham interest, resulting in the return of various members of their families. In the middle of the century the Abercorn interest went into abeyance and in the 1760s the old alliances appear to have broken down; in 1768 Alexander Montgomery and John McCausland were returned with the help of the popular interest.
In 1785 a political commentator described Co. Donegal as follows: 'Wild and mountainous. Great fishing. The county might be governed by the leading interests if they would unite. A popular interest prevailed at the last election (1783). Lord Donegall [Chichester], Lord Leitrim [Clements], Mr Burton-Conyngham (0303), Mr Conolly (0459), have the chief interests. Mr Montgomery(1437) and Mr Brooke (0249) were returned by the independent interest.'130 To this analysis should be added, particularly in the early part of the century, the Gores and the Hamiltons, although in the middle of the century the interest of the Earl of Abercorn (Hamilton) was apparently sleeping; in the 1790s it was enthusiastically revived by his heir, the1st Marquess of Abercorn.131 Among the lesser interests was that of the Montgomerys, who had an estate at Convoy and an interest in Lifford. The eastern part of Donegal had a large Presbyterian interest - the founders of the American Presbyterian Church came from Ramelton - and while this increased the county electorate it also gave it a strong streak of independence, which added to the divisions between the major interests.
In 1768 Montgomery was returned. He was considered to be 'extremely flighty and very independent', and his voting pattern and that of his colleague, John McCausland (1309), who was said to be under his influence, was erratic. Many of the emigrants from this area fought on the American side during the War of American Independence, and Montgomery's brother died an American hero in 1775, thereby ensuring his return in the 1776 general election. Montgomery continued on his erratic path but was returned until his death in 1800. Brooke, who was supported and probably dominated by Montgomery, was also a local landlord returned by the independent interest and described as amiable, 'well-meaning but not a party man'. Montgomery's and Brooke's return was due to the failure of the leading interest in the county to combine, and the strength of the popular interest in the county. By 1797 not even a challenge from the rising influence of the Marquess of Abercorn could unseat them.
Co. Donegal had five boroughs - Ballyshannon, Donegal, Killybegs, Lifford and St Johnstown.