Hello Smiffy,
I am very interested in corresponding with you. I believe you are referring to the 26 March 1857 marriage of my great-grandparents, Elizabeth Mills and John Richardson, parents Edward Mills and David Richardson. As you stated, this marriage was witnessed by Hugh McKinley and Andrew McNutt.
Elizabeth and John Richardson emigrated from Londonderry, arriving 14 May 1857 in Philadelphia. A person named Bell Richardson is listed on the passenger list with them. They went first to New Castle, Delaware where they lived until the late 1870s, moving to Philadelphia. PA. Their deaths are recorded in Philadelphia, John in 1904, Elizabeth in 1906.
I am descended from Ada Grace Richardson, the youngest child of Elizabeth and John Richardson. Currently, I am reading though the microfilmed Dunfanaghy Petty Session records and transcribing information for all Mills, Richardson, Andrew/Andy McNutt, and Hugh McKinley references.