The pilgrimage to Mecca, or Hajj, has been a yearly phenomenon of great importance in Muslim lands for well over one thousand years. Each year, millions of pilgrims from throughout the Dar al-Islam, or Islamic world, stretching from Morocco east to Indonesia, make the trip to Mecca as one of the five pillars of their faith. By the end of the nineteenth century, and the beginning of the twentieth, fully half of all pilgrims making the journey in any...