The prophet Mohammed received the first revelations of the Koran, the Muslim holy book, in a cave on the outskirts of Makkah in 610, launching the Islamic faith. By the end of the century, Islam had spread throughout the Arabian Peninsula and into much of Northern Africa. The map to the left shows the initial spread of Islam with all of the areas being Islamic, save the dark gray of Europe and the cross patterns of Western Africa and Asia. This sudden conversion and continued spread of Islam has established a base of Muslims enthusiastically preforming the Hajj year after year.

Today, Islam is the world's second largest religion with adherents numbering over one billion. It is also the only world religion that is still growing. Because of the prominence of Islam, Makkah has flourished as the spiritual center of Islam. Pilgrims to the Hajj increase every year in accordance with the growing numbers of Muslims and the affordability of travel.