History is one of the most popular majors for law students. Why? First off, the history major is all but useless without an advanced degree. Second, much of history is legal history. Third, much of the law is the culmination of experience--the value of appreciating history is obvious.
I was a history major. If I could do undergrad over again (and if I were solely concerned with preparing myself for law school), I'd have done a double-major in econ and philosophy, but I did just fine. Writing and critical thinking (assuming your program required that of you) are essential, and a history major prepares you pretty well for that.