"Availability of fish and furs" would be the best option from the list, not only because they existed in higher quantities in this area, but because the human population density was still low, meaning higher populations of finish and animals.
Availability of fish and furs was an incentive for profit to settle the Missisippi Valley region. Any good settler knows fancy furs and fresh fish will always fetch a high price. And high prices mean better profits, or money made from the sale of goods or services.
The Commerce Act forbade discrimination against smaller markets, and since they were a part of smaller markets, this favored the farmers. Farmers were also able to transport their produce at reasonable rates.
The general consensus amongst the Civil Rights leaders during World War II was that the fighting in World War II would advance the cause of the Civil Rights movement as people would see the paradox of discriminating against the very people who were helping to protect American values by fighting for their country.
