From its first election in 1542 until some time before 1715, the constituency consisted of a number of boroughs within the historic county of Brecknockshire or Breconshire in Wales.
The original scheme was modified by later legislation and decisions of the House of Commons (which were sometimes made with no regard to precedent or evidence: for example in 1728 it was decided that only the freemen of the borough of Montgomery could participate in the election for that seat, thus disenfranchising the freemen of Llanidloes, Welshpool and Llanfyllin).
One ward of the principal borough was an exclave; namely Trecastle, in the township of Llywel eleven miles west of the main town.
Brecon was little affected by the upsurge of radical politics in the 1860s apart from the one occasion in 1866 when Thomas Price, the prominent nonconformist minister, intervened in a by-election contest to compel the Liberal candidate, the Earl of Brecknock, to issue an address more strongly in favour of reform.
This did, however, result in one of the most tumultuous elections in the history of the borough, which included a torchlight procession and lively meetings at which speakers struggled to make themselves heard.
[2] On election day it was generally accepted that supporters of the Conservative candidate, Howel Gwyn, had been caught engaged in bribery.
[3] His unseating by petition in April 1869 indicated how Brecon largely remained a closed borough, dominated by the politics of influence.
Where the name of the member has not yet been ascertained or (before 1558) is not recorded in a surviving document, the entry unknown is entered in the table.