What factor was the biggest contributor to the birth of sectionalism in the country?
-increasing feelings of nationalism
-the need for trade with other countries
-economic differences between the states that accounted for varying desires and needs from government
-opinions on tariffs

economic differences between the states that accounted for varying desires and needs from government

Explanation:

The economies of the North and the South had been completely different since the start o the colonization in North America. While the Northern economy focused on trade and industrial production, the South centered on cotton plantations that by 1860 produced almost 70% of the world's cotton stock with the labor of enslaved people.

Tariffs and the development of the railroad brought disputes about the government priorities following the needs of one section over the other one.