"The big surprise; however, was that he also discovered that over 50%, (I can't remember the exact number, but I believe it was closer to 70%) of the large commercial Delta plantations were owned by first or second generation Northerners. Many of them had family relationships with Northern textile mill owners and operators. The student discovered that many of the Delta plantation owners left or sent their families North during the war. For that reason, they were unavailable for military service."

Not to me. I've been finding this to be true in my research of the plantation belt from Baton Rouge to Memphis. Large, rich plantations with absent owners who lived up north.

-Natchez area was ripe with northern plantation owners.
-In Mississippi the 1860 Federal slave census cannot be used to count the total number of slave owners because of the flaw of counting the same slave owner multiple times in different counties and states. Many of these owners cannot be found living in the state.
-Short lived co-op owned plantations owned by northern investors with northern banks holding the morgages. (I believe N.B. Forrest got his money via this type of investing)

I am in the middle of researching the amount of distruction to private property in Mississippi during the war and I keep finding references in the O.R. of Union reports naming the owners of certain plantations as well known northern men.

It makes sense. Mississippi was a land speculators dream in the 1850s, and with the river for transportation, investing into a few hundred slaves to work the fields for very large return was a good idea. A northern investors would take a vacation down the river to check out his plantation, and when it got too hot, go back to colder climates. Riverboat trips were the rage at the time and only made the plantation experience that more enjoyable to the rich owners.

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David Upton