To OP, It is important that you consider graduate rankings, because they will tell you, roughly, the strength of each department. But remember, they are usually peer-reviewed rankings that are largely (sometimes all of it) based on faculty reputation and research.
There are schools where they have good faculty but have average programs. There are schools where they have excellent programs but have average faculty. Many people choose former but it is important that when you have to pick between these two you pick the latter.
See what calculus classes they offer. Will you have to take classes with engineering students? Do they offer graduate courses to undergraduates? What classes do they require for majors? What kind of places do graduating students go to? Do many of them go to graduate schools?
These are kind of questions you should be asking. Graduate rankings do help, but they ignore those without graduate programs. Usually presence of graduate program means more research, but research you can do as undergraduate is limited.
Also don't be disappointed if you cannot get into one of the best programs. I know people who went to average state universities and they did well. If you are looking to go to graduate schools, at the end only your drive and knowledge will matter.