Answer:
They were important because they held vital transport links and were important for the economy.
Step-by-step explanation:
The Union believed that these non-participatory States were important due to a number of reasons. Firstly, they were large land holdings which were important for the economy of the union. Apart from that, they served as very important transport links for both export and import of goods.
Both the Union and the Confederacy believed that these States were important.