Besides the other routes unc mentioned, there are jobs available in the field of historic preservation. These include curators at museums, working for the Feds in conjunction with any of the national parks/sites, and other opportunities.
I changed majors in my junior year, from Recording Industry Management to Psychology of all things. I kept RIM as a minor because I didn't want all those classes to be wasted. To that end, I will tell you that if you are like the vast majority of college students, you will end up taking classes that don't fit from time to time. It happens. As a safeguard, I would sign up for the history class, then if you decide not to go that route you've only taken one unnecessary class...far fewer than most graduates will take I assure you. Plus, if you enjoy the class and learn from it it isn't really wasted now is it?
From conversations with you and posts I have seen from you, I get the impression that you are a bright girl. You seem goal oriented. Both traits will serve you well in college, and I have every confidence that you will do fine regardless of taking this class or not.
One final tidbit...I learned a whole lot more outside a classroom in college than I did inside it. Enjoy the experience. Take advantage of it. You are about to be exposed to things you will never again be able to be part of. College is the true melting pot of cultures, beliefs, backgrounds, and personalities. Some of them will be to your fancy, others won't. You will form many opinions and observe several things that will remain with you for the rest of your life. Take it in, from whatever distance or closeness you feel each deserves. Make college a place of real learning.
Oh, and don't party too hard...'specially during your first year.