Hatfield is of Saxon origin. Hatfield House, home of the Marquess of Salisbury, is the most important country house. Aircraft were built from the 1930s when de Havilland opened a factory until the 1990s when British Aerospace closed it. Aircraft design and manufacture employed more people there than any other industry. Hatfield was one of the post-war New Towns built around London. It has modernist architecture from the period. The University of Hertfordshire is based there.