Final answer:
Islam originated in the city of Mecca, now in modern-day Saudi Arabia, the birthplace of the Prophet Muhammad. Medina, where Muhammad and his followers emigrated, also holds significant importance in Islamic history. These two holy cities have been central to the development and spread of Islam.
Step-by-step explanation:
Islam originated in the ancient city of Mecca, which is located in modern-day Saudi Arabia. The city was a prominent trading city well before the time of Islam, already established as a site for religious pilgrimage because of the Kaaba, a shrine considered holy in the pre-Islamic Arabian culture. In 610 CE, the Prophet Muhammad began preaching and organizing a new religion-Islam-in this region. Mecca was the birthplace of Muhammad and is also where he had many of his revelations that would later form the Qur'an.
When considering the importance of cities in the growth of Islam, Medina also played a significant role. After being persecuted in Mecca, Muhammad and his followers emigrated to Medina in an event known as the hijra or emigration, marking the beginning of the Islamic calendar.
The influence of Islam quickly grew beyond these cities, as within a century after Muhammad's death, it was the dominant religion in North Africa, the Middle East, and Persia. The holy sites of Mecca and Medina were united under the language and religion of Islam, which later led to the formation of the Kingdom of Saudi Arabia.