My 2nd great grandfather was Michael McGinnis. He is said to have been born 1805-1807 in Dublin, Ireland. He was m. to Catherine McGuire in Ireland. Children born in Ireland were: Patrick- abt.1826, Edward-abt. 1829, and two daughters- abt.1831 &1834. A daughter, Ellen was born in New York, Dec. 27, 1836. The family inferentially dates his immigration to America between Jan.1835-Dec. 1836, possibly on the Barque Tweed (although no other family members are shown).Bob - For naturalization records you may want to visit the USA section of NaturalizationRecords.com Since your ancestor naturalized in 1844, you will want to look at "Naturalization Records Before 1906". There should be a Declaration of Intent for your ancestor and it will almost certainly have more details such as exact date of arrival, but may not have an exact location of birth.
He lived in Johnson Co., Iowa from 1841 until his death Jan. 11, 1870. I recently found his date of naturalization, July 22, 1844, in Dist. Court, of Keokuk Co., Sigournery, IA. The card only shows his name and country of birth as Ireland. No other information. Do you think there would be a Declaration of Intent record somewhere? I've checked Keokuk Co. clerk and recorder, public library, historical society, and genealogical society, without success.
Be sure to use the interactive map on this page to check for naturalization records specific to Iowa - both online and offline.
If your ancestor arrived via New York, be aware that many of the 1830 arrivals are missing. So finding him or his family may not be possible. Also, they may have sailed into a Canadian port as that would have been much cheaper. Unfortunately Ships Passenger Lists arriving in Canada before 1865 are difficult to find (if they exist at all) as there was no requirement that they be kept.
However there are alternate lists for Canadian arrivals and some passenger lists, which can be found at Filling in the Gaps
If your ancestor did arrive alone on the Tweed (and you haven't told me what your source is for this conclusion), be aware that men often sailed ahead of their family in order to establish a new place of residence. But I had a quick look at some online Passenger Lists and I noted that there were several men named Michael McGinnis (with variant spellings) arriving in the right timeframe to be your ancestor. So I wouldn't be too quick to jump to the conclusion that the Michael McGinnis sailing on the Tweed is yours without some concrete proof.