I'm sure you've already looked at the census records for
John S. Albertson Jr: 1930 Voorhees, Camden Co., NJ; 1920 Camden, Camden Co., NJ; 1910 Camden, Camden Co., NJ; 1900 Philadelphia, Philadelphia Co., PA. His World War I draft card shows he was born in Philadelphia.
John S. Albertson Sr: 1880 Gloucester, Camden Co., NJ (includes sister-in-law Julia, presumably his sister-in-law and not hers); 1870 Centre Twp., Camden Co., NJ. The 1860 census shows a John Albertson 7 with Isaac Albertson 37 and Mary A. 29 living in Delaware Twp., Camden Co., NJ. The same Isaac is in Gloucester, Camden Co., NJ in 1850. Here is one researcher that has Mary's maiden name as Shone: http://wc.rootsweb.ancestry.com/cgi-bin/igm.cgi?op=GET&db=:a25802&id=I13785http://wc.rootsweb.ancestry.com/cgi-bin/igm.cgi?op=GET&db=:a25802&id=I13785
Oddly John and Mary both disappear after the 1900 census.
However, I disagree with them on who Mary's parents were and when she was born.
The 1870 census shows Mary J. Lock 13 with Eliza Lock 39 living in Gloucester, Camden Co., NJ. The family includes Julia P. 7 who was born in PA. Remember Julia living with John and Mary as the sister-in-law in 1880.
I suggest contacting the Cedar Grove Cemetery, undoubtedly Cora wasn't the only family member buried there. Once you have death dates for some of the family members I suggest getting their death certificates which are probably NJ death certificates. I understand you can look at NJ death certificates on microfilm at the NJ State Archives in Trenton. Obituaries will probably help too. John Jr's obit and death certificate should have his mother's maiden name. If not his then any of his siblings' obits and DC's.
Check with the Camden County Historical Society to see if they can help you.