Not that you're doing this for the money, but it's not out of this world. You certainly won’t starve, but considering the amount of education that was required of you in order to become qualified to teach, the hard work and dedication you put into it, and the importance of the job you are doing, it’s a pittance. If you can hang on until you become tenured, especially at a private university, the pay is much better. History professors are some of the lowest paid postsecondary teachers, however. Mainly because there aren’t a lot of job opportunities for people who can list all of the U.S. Presidents and Vice Presidents in order of service.
How much you make depends on the school, whether you're in a fairly urban area or not, and how advanced you are in your career. Some professors work as adjuncts, getting paid only a few thousand per course and making only 20k or so per semester. If you're a full-time professor, you might start out at around 45-50k, then closer to the 60-70k range once you've made tenure. If you hang on long enough (and trust us, some of those history professors get insanely old, to the point that half the material they are teaching is from experience), you can make upwards of 100k, but that's a rarity unless you're also serving as a dean or department chair. But at that age, you may have enough of a hard time getting up out of a chair, let alone being one.