This collection documents the later life of Irish political activist, author, and editor John Boyle O'Reilly during his years living in Boston, Massachusetts. Materials include his artifacts, correspondence, hand-written poems, sheet music for the musical setting of two of O'Reilly's poems, and the scrapbooks he assembled to document his literary career. O'Reilly's correspondence is mostly on letterhead from The Pilot and generally relates to his... editorial work, but also covers his political concerns. Of note are his ongoing correspondence with George Cahill, Jeremiah Rossa O'Donovan, and Francis Henry Underwood; there is also a letter O'Reilly received from Ralph Waldo Emerson. Amongst his writings, highlights are a bound, corrected manuscript of his epic poem "America" and a published 1879 speech he gave to the Boston Press Club.

The collection also contains materials by others concerning O'Reilly, including a biographical manuscript; correspondence by his peers; manuscript and published articles; speeches; and tributes by Massachusetts organizations to which he belonged.