Mohammed was born in the Arab trading and pilgrimage city of Mecca,
in the Arabian peninsula, between
570 and 580 AD. His parents were part of
a family of traders, not among the
ruling families of Mecca, but certainly not poor either. Mohammed himself
however grew up poor, because both his parents died when he was still
very young. Probably his grandfather brought him up.
When he grew up, Mohammed married a wealthy widow named Khadija, whose first husband had been a trader, and so he became well-off again. Probably he became a trader himself.
When Mohammed was almost forty, he said he had heard an angel from God speaking to him for the first time (compare the story of Moses). The angel, Gabriel, told Mohammed that there was only one God, that it was wicked to worship idols (statues and images of gods), and that the end of the world was coming soon, with the Last Judgment. All of these ideas were already common in Mecca, where there were some Christians and many Jews, and presumably also some Zoroastrians. Mohammed also heard Gabriel telling him the words of the Quran.
At first the Meccans seem to have felt that Mohammed's preaching was harmless, but later, as he got more support from the lower classes, and really began to say that people should not worship the old gods, the upperclass Meccans threw Mohammed out of town (like Zoroaster). This was partly because toll collection on trade in Mecca involved traders giving gifts to the gods in their temples on the way into and out of town, and so Mecca stood to lose a lot of money if people stopped giving gifts to the gods. In this sense Mohammed's early preaching can be seen as a tax revolt as well as a religious revolution. People beat up and even killed his followers, who began to be called Muslims. Some of them fled to Ethiopia. Mohammed himself fled to the nearby town of Medina, a farming town where Arabs of various tribes lived together with many powerful Jews and some Christians. Mohammed's flight to Medina in 622 AD is called the Hejira (hej-EYE-rah) in Arabic, and it is the date where the Muslim calendar begins.
Mohammed gathered a following in Medina, though he failed to convince the Jews to join him as he had hoped. There were many refugees in Medina from the breaking of the great dam of Ma'rib, and many of them supported Mohammed. In 630 AD he returned to Mecca with an army and conquered it. After he won another victory against Arabic tribes in 630 AD, other Arabic tribes began to send messengers to Mohammed to say that they would submit to his rule, because he was so successful that he must have God on his side. Mecca, as the holy city of the new religion, ended up doing very well from people coming there on hajj.
Learn by doing: what year is it now in the Muslim calendar?
Go on to the Umayyad Dynasty