Thank you all for your immediate, thoughtful and thorough responses! I am overwhelmed!
Your observations, insights, links and leads are extremely helpful. The lack of records for this family has been a primary problem in Ireland, Scotland and in the US. Our only source of information before 1820 is a "Pennell Book" authored by their grand niece in Trafford, Pennsylvania in 1925, and we have come to doubt some of that. And you are correct, we have been forced to share much that is not documented. Early US records are sketchy and inconsistent. Possible 'cousins' input has been largely contradictory to what has been passed down to us.
So you can see our cry for help wasn't unwarranted, and our appreciation is vastly understated!
That gives what clues??
Full Disclosure: dartman happens to be my uncle, and we are collaborating on the Pennell genealogy project.
That being said, hallmark, my apologies in behalf of our family if someone expressing his gratitude for the quick responses somehow offended you. Since you want clues, here are the best ones I can think of:
The Pennell family of Northern Ireland is mostly situated in the Belfast, Larne, and Enniskillen areas. The Pennell family in that area is distinct from other Pennells in Ireland, as they appear to have originated in the Strathclyde region of Scotland (Renfrewshire, Lanarkshire, Ayrshire and the Kintyre Peninsula). The other "Dublin Pennell" and "Cork Pennell" families have their ties to the Pennells of Devon, Nottingham, and Sussex as far as can be ascertained through the extensive family records of those branches.
The clues that we have gathered so far, including U.S. Census, Birth, Marriage, Death and Cemetery records (all of which are not infallible, it is true) indicate that Robert & Rosannah emigrated to the United States not later than 1818. Several of their sons and daughters were listed as being born in Ireland, or Belfast proper. They may or may not have traveled under assumed names to Philadephia Pennsylvania on the Ship George in 1817. This is a thorny question, as the ships manifest lists most of the given names, but not surnames. Moreover the baggage manifest confirms these names are associated with several trunks. That Robert and Rosannah arrived with several (3 or 4) trunks of linen on the Ship George is a family assertion that predates access to the original manifest. (I know too well that the names may be a coincidence, that the manifest may have entry errors, or that the surnames they took in America may be spurious...)
If naming traditions hold true among Gaelic society for the period, Robert Pennell Would have named his son William, after his own father. The names Robert, James, John, Mary, William, Margaret, and Thomas are recurring in the family, just as they are in both the Pennell families of Western Scotland and Northern Ireland. We know of several William Pennells living in Raloo, the most documented one having been born in 1818 and who served as a executor of several wills before his death in 1892. Whether he would be Robert and Rosannah's nephew is of course pure speculation at this point.
Additionally, we know that some of the family held to Methodism, and some to Scots Presbyterianism and that Robert was supposedly in the Linen trade. Furthermore, some Pennells of Scotland were weavers and sailmakers by trade, but there has been no connection other than that of proximity and general time period.
We know that other Pennell families immigrated to Charleston, Anderson and Abbeville Counties in South Carolina from Antrim in the first quarter of the 19th Century, but there is no solid connection to our Pennell branch of NW PA/NE OH (any old letters and diaries on our end have been lost to the ravages of time). Some of these Pennell may have traveled back to Ireland in the 1830s-40s for reasons of family business.
Whether the Larne Pennell family is the major branch is one thing we are trying to establish, as I especially suspect that the 1803 Ag. Census record indicates a branching out away from the main family, for business or marital reasons. Another question is if the Pennells of Northern Ireland are Scots who arrived in Ulster in the mid to late 18th century.
Again, I apologize for his exuberant thanks, but we had given up hope that there would be any forum that could corroborate or augment our research; the ancestry boards and genweb are well nigh ghost towns for us these days.
Sincerely,