John McElroy 
Struggle for Missouri [EPUB ebook] 

Excerpt: "Whatever else may be said of Southern statesmen, of the elder school, they certainly had an imperial breadth of view. They took in the whole continent in a way that their Northern colleagues were slow in doing. It cannot be said just when they began to plan for a separate Government which would have Slavery as its cornerstone, would dominate the Continent and ultimately absorb Cuba, Mexico and Central America as far as the Isthmus of Panama."