A far more thriving institution resides in the tiny hamlet of Cooperstown, New York: baseball's ostensible birthplace. The Baseball Hall of Fame honors the game's greatest players, where its members are immortalized by bronze plaques. Like Mecca to the Muslims, a pilgrimage here once in a lifetime is essential for any baseball fan.

Baseball represents an essential part of the American character, making it worthy of historical attention. But our interest here is quite specific. Baseball is uniquely suited to quantitative analysis, a sport that has maintained a comprehensive statistical record spanning more than a century. The rules of play have remained relatively fixed over time, making it a meaningful question to ask whether Babe Ruth (1895–1948) [434] or Barry Bonds (1964–) [2217] was a better hitter, and Walter Johnson (1887–1946) [4303] or Randy Johnson (1963–) [6057] the better pitcher.

Statistical measures can be used to judge whether the best players have been recognized by the Baseball Hall of Fame. Objective measures of significance are rare outside of sports, so baseball's statistical record creates an excellent laboratory to study the forces of fame and canonization. Did the right players get selected for the Hall of Fame? Which deserving candidates have been forgotten? Who has been immortalized standing on feats of clay?

This statistical record makes baseball another test of our historical significance rankings. In principle, our Wikipedia-based significance rankings should reflect the statistical record left behind by each player's on-field performance.

Here we give a brief description of the 100 most significant people in history, so you can refresh your memory on any of them who seem fuzzy. But first a confession, to give credit where properly due. These definitions have been edited down from the first paragraph of each person's Wikipedia article. We have tried to capture the essence of each article in a text short enough to be sent over Twitter, i.e., at most 140 characters.

Adams, John [61] (1735–1826) was the second president of the United States; he also served as an American lawyer, statesman, diplomat, and political theorist.

Alexander the Great [9] (356–323 B.C.), the King of Macedonia and conqueror of the Persian Empire, is one of the greatest military geniuses of all times.

Ali [89] (598–661) was the cousin and son-in-law of the Islamic prophet Muhammad, and ruled over the Islamic Caliphate from 656 to 661.

Alighieri, Dante [96] (1265–1321) Durante Alighieri, commonly known as Dante, was a major Italian poet of the Middle Ages.

Aquinas, Thomas [90] (1225–1274) was an Italian theologian who is remembered for his attempt to reconcile faith and reason in a comprehensive theology.

Arc, Joan of [95] (1412–1431) was a French heroine and military leader inspired by religious visions to organize resistance against the England.

Aristotle [8] (384–322 B.C.) was a Greek philosopher, a student of Plato, and teacher of Alexander the Great.