I went to PBS's gorgeous site on the Mexican-American War for information on Zachary Taylor, but got much more than I intended! I expected to see Polk listed under biographies since this was during his presidency, but there as well were Tyler, Lincoln and Grant. So why are all these Presidents associated with this war?
Well, we all know why Polk was there - this has been called "Mr. Polk's War." Polk went into the White House intending to annex Texas, which he did, but that ended up also meaning going to war with Mexico.
Taylor, of course, was one of the commanding generals. His fame from this war would propel him into the White House as Polk's successor. Interesting fact about Taylor - one of his daughters (Sarah Knox) married Jefferson Davis. Taylor was against the marriage because Davis was in the army at the time and Taylor didn't want his daughter to have to deal with what his own wife had had to. Sarah Davis died after just 3 months of marriage of malaria.
John Tyler actually started neogotiations for Texas, but would have to leave the final work to his sucessor.
Lincoln was a freshman Congressman who came out vocally against the war and Polk. He lost the next election.
Grant was a junior officier serving under Taylor. This war made an important impression on Grant and the lessons learned here would eventually be used in the Civil War. By the way, I rather like this picture!
So go spend some time with the Mexican-American War!