I believe they owned the all the surrounding land, and the family used this property for their summer vacations & retreat. My understanding is that the land was donated to the Diocese of Scranton. The real answers are likely with Father Kelly.
You can find authoritative answers to your question at The Library of Congress Preservation Web site. http://www.loc.gov/preserv/
Normally the III means that "John Doe III's" father and grandfather are named (grandfather) "John Doe Sr." and (father) is named "John Doe Jr.". Which would change their names to "John Doe I" and "John Doe II" when "John Doe III" is named. The naming can also skip a generation or even a nephew or grandnephew can continue the name. I have seen the use of the roman numeral system with female names also.
McGiffert/McGifford is a family lineage apparently beginning in Scotland to Strangford Lough in Ireland and then to America. It appears all caucasian McGifferts in America are related to this one family though there was probably more than one emigration from the old country. The earliest McGiffert buried in America is in Greene Co. New York Leeds Cemetery is John McGiffert 1793 -1873. The earliest McGiffert buried in Ireland is in a church graveyard in County Down (Killyleagh - Strangford Lough) and is listed in ancestor John McGiffert's records as coming over from Scotland (Gifford?) 1603 - 1607 to Portaferry Down as part of the Plantation of Ulster. It is significant that this church was a non-subscribing Presbyterian church, possibly accounting for the variation in spelling of the surname.
The northern American McGifferts distinguished themselves with religious scholarship and critical appraisal of Christian orthodoxy. The southern McGifferts prospered in Alabama cotton. Abolitionism no doubt split the family as it did the Presbyterian Church, with one McGiffert dying for the Union and one for the secessionist slave owners.
African American McGifferts can trace their roots to Greene County, Alabama (Eutaw).
If you are referring to the Senator running for president, it appears that his parents are from the USA by the genealogy on http://www.gedview.com/biden/.