If I should mention it then what should I write about it or how should I link it with the rest of my statement of purpose?
(I just suck at courses like history and other core humanities and courses which require you to rote learn a lot of stuff)
I don't know if I'm 100% suitable to answer your question, since I have never applied to a US university; however, I can tell you for sure that in all personal statements I've written for UK universities, I've never mentioned my grades. I don't personally see the point in writing about your grades, since they can find out from your transcripts and from the academic references.
I had the same issue a couple years back when applying for graduate school at the University of Texas at Austin. Their program required a minimum GPA of 3.4, and my overall GPA was below that while my major GPA was higher.
During the online application process, I remember they specifically asked for each type of GPA, which required me to calculate my major GPA on my own (based on unofficial transcripts). So that's one potential route to indicate your higher major GPA, and it suggests that at least some people are interested in that information. This was in an online form, but I still mentioned my sub-par GPA in my SOP.
If you're not provided that avenue, then they may not really be interested in it. However, I don't think it would hurt to mention it in your statement of purpose. Both in academia and the workplace, it's worthwhile to admit to your faults. Eg. 'I had a really rough time in my second year at university, but I was able to turn it around and earned As in later years' or 'I have worse scores in some classes, but always performed very well in major-related coursework'.
Saying something to that effect on a SOP would help them understand that you're ready for graduate school, even if you don't have a blemish-free record. If you can follow it up with strong GRE scores and strong recommendations, then (from what I've heard) many admissions committees will be more lenient on GPA.
I don't personally recommend putting it on your CV. I tried doing that by putting "Major GPA: x.xx" under "GPA: y.yy" and it seemed to confuse people more than anything else. It's really not standard to differentiate the two, so anyone who hasn't seen that before will wonder why you're doing that. The SOP uses plain language and allows you to explain yourself, so it seems a better fit for this kind of information.
Overall, I would devote maybe 1-3 sentences on this point in your SOP; you want to focus their attention on your strengths, after all.