http://teachingamericanhistory.org/library/index.asp?document=949 A little known fact of History is that when the US was fighting our own Civil War, Mexico was going through there own upheavals, and in fact, Abe Lincoln was opposed to the Mexico/American war in the 1840's. In fact, Juarez and Lincoln exchanged letters during the turmoil of the period, it is an odd fact of history: http://www.olvera-street.com/html/president_benito_juarez.html
well the political party Lincoln was apart of at the time of the Mexican War(the Whigs) as a whole despised the war as they felt it was essentially imperialism with the goal to further spread the institution of slavery which the Whig party felt for the most part needed to be stopped at where it had currently existed.