I want to say, "I like history in general." How would I word that in Japanese? I can say, (Watashi wa) rekishi ga sukidesu, but I'm not sure how to say "in general."
So by "in general" in this case you mean: you like all parts of history more or less equally, not just one specific part or era? (There are other meanings of "in general" such as "in most cases", so... just making sure)
In that case you can use the suffix ～全般 (zenpan) to indicate the entirety of something including all its parts:
私は歴史（学）全般が好きです。 watashi wa rekishi(gaku) zenpan ga suki desu
(my first thought was that you would need 学 to indicate liking the study of history instead of liking "everything that happened in the past", but Google searches appear to indicate otherwise...)