To determine the most logical addition to the paragraph, it would depend on the context and main argument of the paragraph itself. However, if the focus is on illustrating the repercussions of the war, specifically related to slavery and its expansion, then "information showing how much slavery spread as a result of territory gained during the war" would be a strong addition. This would directly address the implications of the war in relation to slavery, which is often a significant point of discussion in historical analyses of the conflict.
If the paragraph discusses justification for the war or different perspectives on it, then the quote from President Polk would be relevant. However, if it's analyzing the overall sentiment among the populace regarding the war, then information about public opinion would be more fitting.
In summary, without knowing the exact context of the existing paragraph, the best choice for highlighting the consequences of the war would likely be:
information showing how much slavery spread as a result of territory gained during the war.