D&C 93:53 - "And, verily I say unto you, that it is my will that you should...obtain a knowledge of history, and of countries, and of kingdoms, of the laws of God and man, and all this for the salvation of Zion."
If we fail to obtain knowledge in these areas, we are in trouble spiritually, because we aren't obeying a commandment of God, and temporally, because the decisions we make in ignorance (what policies to support, who to vote for, etc...) will almost never be the correct decisions.
Many of us may assume that we got everything we need from the history and civics classes we had in high school or college. If you fall into that category, consider this: if we relied solely on that same education, we would think that we descended from apes, and that sexual promiscuity is normal and healthy. Not everything that comes out of public education is correct, and we should have no reason to assume that the civics education we received was entirely correct. According to Ether 8:25, the evil one "seeketh to overthrow the freedom of all lands". One easy way for him to do that is to have people who are ignorant of history and laws.
I'm not saying the civics education we got in high school or college came from Satan. I am saying that we have the responsibility to make our own effort to ensure that it was both correct and complete, and to make up the difference if it wasn't. If you aren't sure, any of the books listed at the bottom of this page would be a great place to start looking.