In 1855, at the age of 21, Whistler left America to become an art student in Paris, and his correspondence continued until his death in 1903. Based on records of over 13,000 letters, including copies, surviving in public and private collections around the world, the on-line centenary edition makes available a total of some 10,000 letters covering this period. The edition includes all the letters written by Whistler and all the letters written to him; letters mentioning Whistler are also included on a selective basis. The Whistler correspondence constitutes a highly important source of information, not only for the artist himself, but also for the study of European and American art in the second half of the nineteenth century, recording his contacts with fellow artists, dealers, collectors, literary figures, and a wide circle of acquaintance in Britain, the Continent and America. No other artist of the period has left such an extensive record of his career.