Prison Forts are penal structures dating from the 15th to 18th centuries in Pretany, constructed due to the Declaration of Ingerish Penal Ownership, imposed by Ingerland in 1410. The forts, numbering around 300, are in various states of ruin and decay, with few left standing as historical landmarks in the kingdom. They were built to hold in total nearly 400,000 prisoners with crimes of varying severity. The forts, although imposed upon Pretany and built by the ingerish prisoners themselves, are a permanent fixture in Pretanic culture and lore. Many of the forts expanded into villages and towns as the ingerish military did little to support, finance, and guard the structures. In the 355 year occupation of Pretany by Ingerland, the forts became the launching point for the spread of ingerish culture, language, and place names throughout the kingdom. The four most well known and famous forts that expanded into bustling cities due to lack of supervision are Port Welsh in Welshire, Port Southsmith, and Port Dash in Augustside, and Port Battle in Firgotonus. All four cities started as makeshift landing ports for ingerish prison ships, with the forts constructed on site. The entire shire of Welshire is said to be an expanded ingerish "settlement" in the heart of Romantian or Nortian Pretany. The prison forts of Croxton Northwall, Ancient Heathoak, and Aderland were also settlements that expanded organically and unsupervised during the mid 16th century and helped spread ingerish culture. Pretany advanced into the industrial era with the production of the largest forests within the region. Pretany had always been a frontier of Uletha, but as population expanded by 1650 the inland forests were being quartered off as both royal forests and timber land, lumbered by Ingerish prisoners. Millions of acres of the country were converted to practical use and by 1700 most of the virgin forestland had become home to the largest state run timber production line in the world. Their labor secured land holdings in the prison fort regions and settlements for the prisoners and their families, ensuring their freedom from regulation by the crown, protection from crack-down by the ingerish military, and their place in pretanic society. When the Penal Trade Agreement of 1765 was drafted all further fort construction was halted and the cities were left in control of the local governments, many formed exclusively by the ingerish people there. The ingerish population then became full pretanic citizens officially.