Why was the Ohio Valley so valuable?

BankChampaign, National Association 1 Brickyard Bank 3 CLEAR FORK Bank National Association 1 Commonwealth Community Bank 13 FIRST HARRISON Bank 9 FIRST MW Bank OF THE OZARKS 14 First National Bank & Trust 8 First National Bank of Colorado 4 First National Bank of Fleming 10 First Natural State Bank 4 First State Bank of Forsyth 2 FIRST SVC Bank 5 Great Nations Bank 1 Maquoketa State Bank 4 New Valley Bank & Trust 1 Peoples State Bank of Munising 4 PRIMEBANK 13 Southeastern Bank 6 Stifel Trust Company Delaware, N.A. 20 Vergas State Bank 2