At this time Holland was also a trustee of the Pennsylvania College for Women (now Chatham University), where he taught ancient languages.

His trip to Argentina in 1912 to install a replica of a Diplodocus, at the behest of Carnegie, is told by Holland in his 1913 travel book To the River Plate and Back.

[5] The Diplodocus campaign earned him his share of international recognition as well, in the form of a French legion d'honneur and a German knight's cross, among others.

He supported active collectors worldwide, obtaining major collections from previously uncollected regions between 1890 and 1930 through the efforts of William Doherty, Herbert Huntingdon Smith, H. L. Weber[7] (1873–1962), J. Steinbach[8] (1876–1930), S. M. Klages[9] (1875–1957), and many others.

Holland was also interested in the history of his forebears, particularly that of his Moravian and Huguenot ancestors in Bethlehem, Pennsylvania, Philadelphia, England, and France.

He amassed a considerable amount of material, comprising letters, diaries, portraits, and other artifacts, and donated it to the Historical Society of Western Pennsylvania in Pittsburgh, now known as the Senator John Heinz History Center.