Ewloe Castle was a native Welsh stronghold built by Llywelyn ap Gruffudd following his seizure of much of modern Flintshire from the English Crown in 1257. Ewloe was the location of the family's manor, and it is possible that the castle occupies a site fortified earlier by Owain Gwynedd or Llywelyn ab Iorwerth with an earth-and-timber stronghold.
Ewloe occupies a narrow ridge below the lip of the Wepre Brook valley and was constructed of local yellow sandstone, possibly in two phases; the first consisting of a Welsh Tower and oval stone walls, then followed by the addition of a lower court with a further stone curtain and western tower. There is no obvious access between the two courts and it is possible that they operated separately, each accommodating a single princely entourage.
Following the succession of Edward I in 1272 Llywelyn failed to answer five summonses to do homage to the new king, who declared his intention to go to war against the proclaimed rebel. Within a year the Prince of Wales had been defeated; the castle fell to the English and was never to be used again as a fortified stronghold.

Source: Renn, D. and Avent, R. 2001. Flint Castle & Ewloe Castle: Cadw Guide (Second Edition)

K. Steele, RCAHMW, 4 November 2008