The land was called Merestun, settlement by the mere, when the Anglo-Saxon Gunnfrothr held it before the Conquest. William FitzOsbern, William the Conqueror's closest friend and the first Earl of Hereford, raised the original castle here around 1070 to anchor the new Norman lordships along the Welsh border. FitzOsbern was killed in Flanders the next year. His son joined the Revolt of the Earls in 1075 and lost everything, including Wigmore, which William I handed to a supporter named Ralph de Mortimer. From that day forward Wigmore was Mortimer ground, and the Mortimers would shape British history for three and a half centuries from this ridge.

The Mortimer who matters most is Roger, born in 1287. He inherited Wigmore in 1304, married the heiress Joan de Geneville and acquired Ludlow Castle and vast lands in Ireland with her. By the 1320s he was the most dangerous of Edward II's enemies. He escaped the Tower of London in 1323, fled to France, and became the lover of Edward's estranged queen, Isabella. Together they invaded England in 1326, deposed the king, and probably had him murdered at Berkeley Castle. For four years Roger Mortimer was effectively king of England in all but name, stepfather to the boy Edward III. In 1328 he held a tournament near Wigmore that almost every magnate in the kingdom attended, a deliberate statement of power on his home ground. Edward III tolerated him until he was old enough to act. In 1330 the young king's men seized Mortimer in Nottingham Castle, tried him for treason, and hanged him at Tyburn. His lands were forfeit; the family did not get Wigmore back for twelve years.

The Mortimers married into royalty after that. Edmund Mortimer married Edward III's granddaughter Philippa, and in 1381 their six-year-old son Roger was declared heir presumptive to the throne should Richard II die childless. That claim, carried through the female line, eventually descended to Richard, Duke of York, through his mother Anne Mortimer. When Anne's grandson Edward of March was based at Wigmore in early 1461, gathering an army from the family heartlands in the Marches, he was operating from the castle of the lineage that gave him his crown. From Wigmore he marched south to fight at Mortimer's Cross, named for these same Mortimers, and ten weeks later he was Edward IV. The wheel had turned: a family that had failed to become kings had instead produced one.

By the time of the English Civil War, Wigmore had passed through Elizabeth I's hands to the Harleys of Brampton Bryan. Sir Robert Harley sided with Parliament. With her husband away in London, Lady Brilliana Harley made the decisive call: rather than risk Wigmore being seized by Royalists, she had its defences dismantled herself. The castle was left in ruin, vegetation took over, and unusually for a major British site it stayed in private hands through the 19th century, escaping the heavy-handed clearances that scrubbed most other ruins clean. Today the curtain wall still stands at near full height along the east and south sides between the south tower and gatehouse. The keep mound and the inner bailey are wooded. From the air the site reads as an oval crown of green and stone above the village, a ruin still being slowly reclaimed by the country it once helped to rule.