Shortly after Houghton's death, his correspondence and other papers were entrusted to Arthur Edwin Scanes, who 'classified and catalogued' them; this work is praised by T. Wemyss Reid in the preface to his Life, Letters, and Friendships of... Lord Houghton, and it is likely that the labelled paper files which can be found throughout the collection are his work. Notes by Scanes on documents such as 'found with 1874 letters' (HOUG/227/65) suggests that Houghton kept at least some of his correspondence filed chronologically, and that it was Scanes who arranged them by correspondent.
A list by Scanes: 'Correspondence of the late Lord Houghton | List of Boxes and their Contents', describing three boxes worth of material, can be found at HOUG/HC; not all the papers described there can be matched with items now in the collection, and reference is made to family letters 'already handed over to the present Lord Houghton'.
When James Pope Hennessy was given access to Houghton's papers in the 1940s to write his two-volume life, he describes them as being 'housed in twelve japanned-tin deed boxes' (preface to Vol. 1., 1949); in the preface to his second volume (1951), he mentions 'a mahogany chest, apparently unopened since the period of the Franco-Prussian war, and continuing upwards of four thousand letters which Wemyss Reid could not have seen'.
Immediate source of acquisition or transfer
A first accession was given to Trinity College by Lady Crewe, wife of Houghton's son, in 1959; a second was given by her daughter the Duchess of Roxburghe in 1974.