It covered a sparsely populated area, and was bounded to the north by Montgomeryshire and Shropshire, to the east by Herefordshire, to the south by Brecknockshire and to the west by Cardiganshire.

The Radnor Forest is an area of high ground covering a large part of the east of former county.

This peculiar Marcher status and its want of Welsh speakers gave weight to the traditional local expression, "Neither Wales nor England, just Radnorsheer"[5] The 1535 act created Radnorshire from a number of former territories, including the cantrefs of Maelienydd and Elfael and the commotes of Gwrtheyrnion and Deuddwr.

The county's poverty was remarked upon thus in the 17th century by an anonymous visitor: Poor Radnorsheer, poor Radnorsheer, Never a park, and never a deer, Never a squire of five hundred a year, Save Richard Fowler of Abbey-Cwm-hirApart from a handful of parishes along the English border the Welsh language remained the first language of the county well into the second half of the eighteenth century.

[9] By 1850 the language had retreated to the western parishes of Rhayader, Llanyre, Cwmdauddwr, St Harmon and Nantmel.

[10] By 1900 Welsh was still spoken by a sizeable minority west of the town of Rhayader, the language disappearing as the century progressed.

Here is found the former county top of Great Rhos, at a height of 660 metres (2,170 ft) above sea level.

The backbone of local incomes was tourism, hill farming and the public sector such as care, education and road/public land maintenance.

Sheep, dairy/cattle and poultry farming provided more revenue than crops which like much of Scotland, the Pennines and Wales received more than national average precipitation and can be subject to late frosts.

Radnorshire was divided into eight UDs and RDs, which were unchanged until their abolition in 1974: From the medieval period until 1974, Radnorshire was divided into civil parishes for the purpose of local government; these in large part equated to ecclesiastical parishes (see the table below), most of which still exist as part of the Church in Wales.

A Shire Hall was built in Presteigne in 1542 and rebuilt in 1829, which served as the main administrative building for the county.

[7] The county council generally held its meetings at the Pump House Hotel on Spa Road East in Llandrindod Wells.

[23] The county council then moved its staff to larger offices at the former Gwalia Hotel in Ithon Road in 1950.

A gold reguardant lion on red was for Elystan Glodrhydd, Prince of Wales c. 1000; black boars' heads on white for his son Cadwgan.

[32] The first election to the council was held in 1973, initially operating as a shadow authority before coming into its powers on 1 April 1974.

It offers open-air and street theatre and music, a fairground, craft fair, historical re-enactment, entertainments at the Albert Hall and exhibitions of old items.

Poverty and agricultural change, decline and industrial progress elsewhere has always made Radnorshire a place of net emigration.

Emigrants employed the name of the county in the United States: Others may have formed part of the Welsh community in Patagonia.