Portarlington was enfranchised by a charter of 19 Chas II, 1668. The corporation consisted of a sovereign, two portreeves (or bailiffs), 12 burgesses and freemen, with the right to elect two MPs. In 1783 it had 3,000 inhabitants, one-half protestant, all holding in perpetuity.333 It had a famous settlement of Huguenots who increased the protestant population. The corporation was controlled by successive members of the Dawson family. In 1773 it was said that the MP, Sir Thomas Butler (0332), 'was recommended to this seat by Lord Townshend, for when Lord Dawson was dignified with a Peerage he offered this seat to his benefactor the Lord Lieutenant, who named Butler and Butler was well with Lord Townshend by always opposing the Burtons'.334 However, Sir Thomas died in 1772 and Viscount Carlow (0597) then brought in his son, Joseph Dawson (0590), who was barely of age. Lord Townshend had hoped in view of Butler's short tenure to fill the vacancy, but Viscount Carlow had five sons and three daughters to provide for. It was confirmed in 1785 that 'This Borough is the property of Lord Carlow by whom both seats were sold (in 1783). Mr Justice Kelly did represent it, but upon his being made a Judge, Sir Boyle Roche on the recommendation of Administration came in for a thousand pounds - half price.'335 In 1785 Lord Carlow (0589) was created Earl of Portarlington. Five years later, in 1790, it was said that:
This Borough has long been addicted to the interest and subject to the control of the Dawson family, who now derive the title of Earl from it. The only electors are the Burgesses, who, according to the established practice, are chosen into their offices agreeably to the pleasure of the Earl of Portarlington who consequently, in effect, nominates the representatives.
Portarlington was not disfranchised by the Act of Union. It continued to send one MP to the united parliament. The franchise remained unchanged. The number of voters was estimated at 63 in 1784, 12 in 1815 and 15 in 1831. Its patron was John, 2nd Earl of Portarlington - his father died in 1798. It was sold in 1802 for £4,000. Its most distinguished post-Union MP was the economist David Ricardo. Ricardo offered a loan of £25,000 at 6 per cent which Lord Portarlington needed to clear the encumbrances on his estate and also for the purchase and disposal of the seat for four years for £4,000. Ricardo died in 1823.