Dartmoor Prison is so well-known as a civilian criminal prison (it has operated as one, on and off, since 1850) that it's often forgotten that it was built in 1809 as Princetown War Prison to contain prisoners-of-war during the Napoleonic Wars. In its early years - marked by appalling conditions that caused the death of around 1500 prisoners - its inmates also included Americans from the 1812-1815 Anglo-American War.
A deal of historical material focuses in particular on the circumstances of the infamous "Dartmoor Massacre" of 6th April 1815, when seven Americans died when a crowd was fired on by guards (it's unclear if a mutiny was in progress, or if the prison superintendent in charge, Captain Shortland, had misread the situation - whether knowingly or incompetently). Within the prison grounds - not open to the public - there's a memorial and American cemetery. The Legendary Dartmoor site has a brief account - Dartmoor's American Memorial - and there are more details, including photos of the site, at the Dartmoor Prison American Cemetery Restoration Project. Pages 28-29 of 1816: America rising (Carl Edward Skeen, University Press of Kentucky, 2003) gives a good account of the effect of the incident on Anglo-American relations. Contemporary texts such as Dartmoor prison; or, A faithful narrative of the massacre of American seamen, to which is added, a sketch of the treatment of prisoners during the late war (James Adams, 1816) and editorial in various magazines such as Niles' weekly register and Cobbett's weekly political register demonstrate the political impact at the time. The New Monthly Magazine's "Dartmoor Massacre!" probably wins for being most polemical.
Basil Thomson's 1907 The story of Dartmoor prison gives a fascinating but harrowing account of the early years of Dartmoor, documenting the bizarre subcultures that sprang up in the overcrowded multicultural conditions. From the preface:
It was by caprice that Fate chose fifteen acres in the heart of the Dartmoor highlands for one of her strangest experiments. Within the double ring of masonry were met men who had been gathered from nearly every nation under heaven to fight against England under the Tricolour and the Stars and Stripes, and were here set to evolve a new social order under conditions that are probably unique in human history. The War Prison was an overcrowded city without women; with its own laws, its schools, manufactures and arts, its workshops where coin could be counterfeited and Bank of England notes forged. In a society composed of persons drawn from every social rank, from the officer of the Grande Armee and the negro general from Hayti to the Sansculotte from the Faubourg St. Antoine, it is not surprising that monstrous growths should be produced, and I do not think that anywhere in history can be found figures so horrible and grotesque as the "Romans." 1 The life of the War Prison, it is true, was not made up of horrors. It throbbed with romance and comedy and tragedy, but on this tiny stage in a short hundred years the play has been an object lesson of the distortion of human nature wrought by war and by crime.
1. An organised underclass of naked scavengers who lived in the cockloft (the structural space under the roof) - they were drawn partly from prisoners who had lost everything, even their clothing, through gambling; and partly from those who had deliberately rebelled against the system.
Again, online contemporary sources confirm the eccentric detail Thomson reports, such as Sporting Magazine's 1813 account of prisoners' regimented sleeping arrangements; the Analectic Magazine's account of the rule of "King Dick", who is recalled in a number of prisoners' journals; and the brief description of "The Romans" in Charles Taylor's The Literary panorama.