The Connolly papers consist mainly incoming correspondence from friends and admirers requesting Connolly's aid in obtaining copies of rare books, soliciting articles from him, or commenting on his writings. Around one quarter of the letters come from historian John Dawson Gilmary Shea. In letters written just before his death in 1892, Shea comments on the progress of his four-volume work, History of the Catholic Church in the U.S (1886-1892). Other correspondents of note include: William H. O'Connell, Archbishop of Boston; and William Byrne, educator and author. Of interest is a 1909 letter from Frederick A. Murphy, a missionary operating in southeast and central China, in which he relates the many arduous and frustrating aspects of his work.