Hi everyone :)
Dorothy, if you're still looking I can confirm that the Siscos were from the same area in Northern NJ as Davenports. Yes, the Davenports lived around Newfoundland area, and while I don't have the records anymore I do remember coming across the name Sisco on local tax lists, deeds, etc. In fact there's still a Sisco Road in Newfoundland today.
Hard thing about researching this area is that it's at the border of three counties: Sussex, Passaic (formerly Bergen), and Morris. Newfoundland is an unincorporated area that is partially in West MIlford Twp/Passaic County and partially in Jefferson Township, Morris County. Before it became West Milford Twp/Passaic County, this area was Pompton Township in Bergen County. Before that it was Saddle River Township, Bergen County. This area bordered Hardyston and Vernon Townships in Sussex County. Jefferson Township/Morris County was previously part of Pequannock Township, Morris County (you probably should include Rockaway Township, Morris County also if researching). Lots of places to look for one area!
I'm descended from Mary Davenport, who first married Anthony Dougherty. I assume they were married by the time their daughter Margaret was born in 1784. Their farm straddled the dividing line of Vernon Township/Sussex County and Saddle River Township/Bergen County in the late 1700's/early 1800's. From Sussex County Deed Book X2, page 60 located in the Sussex County, New Jersey County Clerk's Office records vault I know that their farm adjoined the farm of Leonard Davenport and his wife Mary, and that Anthony's wife Mary had remarried to John I. Smith.
Anthony's wife Mary was widowed on 31 Dec 1813 when Anthony died in the War of 1812, and from the above deed I can confirm that Mary was married to John I. Smith as of 1818. I've read Saveson's "The Autobiography of Archibald Smith and Related Documents" which says Mary was a daughter of Leonard Davenport, but there's a conflicting account in J. Percy Crayon's "Rockaway Records of Morris County New Jersey Families" which says Mary was the daughter of Abraham/Brom Davenport:http://www.rootsweb.ancestry.com/~njmorris/rockawayrecords/d...
Leonard and Abraham Davenport were brothers. I tend to believe that Leonard's her father because that info comes from a family member, and Crayon's was written years after.