A biggie: the transcontinental railroad. Because it would economically improve wherever it was, both the North and the South competed for the railroad to be in their respective territory, evidenced by the Kansas-Nebraska Act and the Gadsen Purchase and induction of California as a free state in 1860.
In addition: people could get land cheap because it was abundant and might leave to start afresh economically.
There's other stuff I can't remember as clearly, but there's a little and I hope it helps :)
Speaking from experience, the answer is not D.
<em>Are you talking about the Constitutional Convention?</em>
Answer:
No, I don't think so. Lots of conferences nowadays have many reporters there to record exactly what you're going to say. In the presidents office, there is always a camera or reporter in there. Back then, they could control that but if we did that now, the American people would riot.