Question

Which minority wielded the greatest political power in its region in the period before the civil war? ship owners in new england laborers in the industrial cities planters in the south farmers in the northeast

Answer 1

Laborers did not have much power since this was also before the age of Unionization. So that leaves them out. 
Farmers throughout history never really had any political power. Since they were viewed as a more localized entity. 
Shipowners for obvious reasons held a certain amount of power. They had a huge impact on importing, and exporting goods, and materials. 
Assuming when you say planters you mean the plantation owners in the South. ( Who were the backbone of Southern revenue.) 
Out of the last two I would tend to believe the Shipowners held more extensive power than the planters.

Answer 2

Answer:

The minority that had the greatest political power in its region in the period before the civil war was "planter in the south".

Explanation:

To understand this answer we have to analyze the context first, so:

In the first place, there were more millionaires per capita in the Mississippi river valley in 1860 than anywhere else in the United States of America. Second, the elite master class of the south created their own culture and social rules. Making arguments to convince ignorant people that what they said was the truth. Third, by having the power they were able to create and define the political circles in the south. Gaining political weight that supported them and their ideas. The cotton boom allowed them to gain more money to keep the power.