Because American copyright law applied only to American publications, European authors were unable to profit from the publication and sale of their works at extemely low prices during the nineteenth century. The so-called "cheap books" movement, spread rapidly by small upstart publishers after the Civil War, threatened the "courtesy principle" of gentlemanly price-fixing adhered to by the large, established publishers such as Henry Holt. By the 1880s cheap books flooded the American market. By 1890 authors, publishers, and printers' unions joined together to support an international copyright bill (