The first part of this book established the general validity of our ranking methods, and used them to illustrate grand themes and processes of history: canonization in textbooks, evaluating the precision of selection processes, measuring the flow of time, and quantifying changes in the perception of gender.

Now we will reduce our focus to the particular. We rank the significance of the world's historical figures in terms of the different niches they occupy: politicians, scientists, religious leaders, artists, actors, outlaws, and even dentists. It is instructive to see who rises to the top of each individual heap, both to refresh our memory on old historical friends and to make new ones. You have our blessing to skim through any group that you are not interested in, but sneak a peek at the ranking tables before you move on.

Some may question how we decide which figures belong in a particular group. Defining exactly who is an actor, an outlaw, or a dentist turns out to be very difficult to do in a precise way. We used the following methodology. We would start from a roster assembled in some book or Wikipedia category, and then amend the lists based on general knowledge and our sense of the nature of the category. No doubt certain omissions remain, although we believe that we have captured most of the usual suspects.

This first chapter concerns America's political leaders, from our presidents down to the mayors of our greatest cities.