Thanks for the response. I think Ireland because my nearest DNA match outside the US is to a fellow in Ireland - unfortunately, his surname is not Bennett.
I don't know Thomas Bennett's trade. He was listed as a "Farmer" in the 1850 US Census. He died on the Oregon Trail shortly after the census was taken. His wife kept a diary but it was burned in a house fire in 1940 (along with the trunk of keepsakes and heirlooms in which it was kept - ouch!). At this point (after searching for 40+ years), I'm hoping for a DNA match. "Bennett" was a pretty common surname in the UK at the time my ancestor, Thomas Bennett, must have immigrated to the US (ca 1830-1840) - making the search all the more difficult. Basically, he sort of sprang onto the scene in 1846 when he purchased land in Iowa. Before that - nothing that I can say for sure was left by or about him. Lots and lots of dead-ends and maybes but precious few "for sures".