An office is a room, set of rooms, or building where the business of a commercial or industrial organization or of a professional person is conducted. In the late 19th century, commercial offices for conducting business first appeared in the United States. The railroad, telegraph and then the telephone were invented allowing for instant remote communication. Wherever manufacturing existed, for example in a mill or factory, the administrative office could now be placed at a distance. By 1900, nearly 100,000 people in the United States were working as secretaries, stenographers, and typists in an office. The average worker was employed for sixty hours per six-day work week. Specialized training was now available for people who wished to study office skills. The greatest symbol of the office is the office chair and desk. No photographer credited, undated.