I have a Ph.D. in history (French) and I can tell you that the advice above is pretty much on the mark. First major in history as an undergraduate, do well, decide what area you want to specialize in, what kinds of historical questions interest you, then take the GREs and apply to a Masters program and eventually a Ph.d. program. Getting the degree typically requires doing original archival research and writing a several hundred page dissertation. From start to finish (from undergrad to Ph.D.) it takes a good 10+ years. Unless you are planning on teaching, it is perhaps not the best way to spend 10 years. But I guess it is a personal choice in the end.