Child labour has traditionally referred to the use of children to perform adult work on farms and in factories and mines. Ironically, it has helped as well as hindered the development of universal public education in the United States. Historically, this problem did not become a controversial social issue until the beginning of the Industrial Revolution in the late 18th century. After a series of wars produced a shortage of adult male labour in Britain, cotton mill owners offered children free room and meals in company-owned dormitories in exchange for their labour. Government authorities were delighted to get homeless children off the streets. For the mills, the introduction of child labour proved one of the most profitable innovations of the industrial Revolution. The practice spread to the United States, which also faced a shortage of adult male factory workers to produce food and tobacco, the staples of the new nation's trade. At the time, most schools were already reserved for the children of landowners, and therefore, an entire generation of child labourers had grown up illiterate by the 1830s. As the quality of goods they produced deteriorated and overseas sales of American goods declined, many of the very industrialists who had exploited child labour at the turn of the century joined social reformers who wanted to end such exploitation, supporting universal compulsory education to ensure that their future workers would be able to read, write and calculate.