Mark Twain's residence from the Fall of 1905 to 1908, when the Stormfield house was completed.  This is where Paine began his biography of Twain.  During this period, in the summer of 1906, he stayed at Upton Farm near Dublin, in New Hampshire.

See Then & Now: A Home Fit for Fifth Avenue (and Mark Twain)

The Lost "Mark Twain House" - No. 21 Fifth Avenue

The Fall of the House of Twain