The great penal reformer travelled widely, inspecting conditions in gaols in Britain and on the continent. It was through him that parliament passed two acts in 1774, one enforcing standards of cleanliness, the other replacing prisoners' fees by jailers with official salaries. In late March 1774 he visited Durham, Newcastle and Morpeth (followed by Carlisle and Appleby). Another visit took place in January 1776, and he was in Newcastle again in June 1779 and March 1782, going on to Berwick on all three occasions.
Howard approved of conditions in Newcastle's Newgate gaol, the cleanliness, the adequate bedding, the good fires, and the humanity of the jailer. There were fourteen felons and ten debtors. He found proper bedding and heating provided at the House of Correction in the Manors. By contrast he was disgusted by conditions in the county gaol, then housed in the basement dungeon of the castle keep:

'During the assizes at Newcastle, the county prisoners are, men and women, confined together seven or eight nights in a dirty damp dungeon, six steps down in the old castle , which, having no roof, in wet seasons the water is some inches deep. The felons are chained to rings in the wall.'

Until 1800, the inmates of such prisons, who might be wholly innocent, were exhibited to the public by the jailer at twopence a head. This dungeon, or guard-room, was in use until modern times. Basil Bunting, the great poet, was confined here as a conscientious objector during WWI.
Howard's book The State of Prisons in England and Wales, with an Account of some Foreign Prisons was published in 1777. The Howard League for Penal Reform, founded in 1866, was named after him.