One of the notables in the Blacker family, Colonel William Blacker, High Sheriff of Armagh, took part in the "Battle of the Diamond" and was a founding member of the Orange Order.This, and subsequent events like the setting up of a 'provisional' Grand Lodge in the town after the 'voluntary' dissolution of the Order in 1825, led to the town being known as 'The Orange Citadel' and was a center of sectarian strife for two centuries.The Troubles led to the town becoming segregated – the northwestern part of the town became almost wholly Catholic/Irish nationalist, while the rest of the town became almost wholly Protestant/unionist.The Troubles also intensified the long-running Drumcree marching dispute, over Orange marches through the Catholic part of town.The Irish Confederate troops abandoned Obins Castle during the Cromwellian conquest of Ireland, and Hamlet Obins (who had survived its capture) repossessed it in 1652. This family's legacy to the town includes street names such as Montagu Street, Millicent Crescent and Mandeville Street, as well as buildings such as the Fergus Hall (formerly the Duke's School and Church Street PS), and the Carlton Home (the Duke's former townhouse, latterly a maternity hospital/nurses accommodation and now private apartments).The Blacker family, descended from Danes who entered Ireland in the 9th century, founded an estate at Carrick, on the Portadown–Gilford road.The park is now bounded on either side by Obins Street and Castle Street, both of which are references to "Obin's Castle".
In 19, the town centre was devastated by two large car bombs planted by republicans.
In the 19th and 20th centuries Portadown was also a major centre for the production of textiles (mainly linen).
Of its population, about 61% are from a Protestant background and 31% from a Catholic background.
In one of the worst atrocities of the rebellion, in November 1641, Irish rebels forced about 100 captured English and Scottish settlers (or 'planters') off the Bann bridge and they either drowned or were shot.
This became known as the "Portadown massacre", and partly precipitated the revenge attacks carried out in Ireland several years later by the forces of Oliver Cromwell.
The project involves teenagers from both of Northern Ireland's main communities.