The National Seismological Archive (NSA) is the United Kingdom national repository for seismological material. It was created principally to preserve data from seismological observatories in the UK that have now closed. In many cases in the past records have been lost or destroyed when there is no longer anyone to look after them; the NSA provides a permanent home for these historical scientific documents, to preserve them for posterity. The principal collection consists of the seismograms stores from defunct observatories; also bulletins and reports from all over the world dating from the 1890s onwards, held in a variety of media, including earthquake-related newspaper cuttings, glass slides, microfilm, and comprehensive UK earthquake research material collected over a 30 year period. One of the major projects of the archive has been the presentation of current knowledge of UK historical earthquake seismology material in a short series of reports, easily accessible to researchers. Data includes: Bulletins and correspondence from historical UK observatories; The Ambraseys collection of papers and notes concerning world seismicity; Reports and bulletins from the BGS seismology group; Collected documents concerning seismographs and UK earthquakes; Paper felt report forms distributed and collected by the BGS for earthquakes from the early 1980s until web based forms replaced them.