Because when Muhammad PBUH left Mecca & went to Yathreb (Al-Madeenah) where he established the Islamic Community, the real Islamic achievements started mostly from that time. This is the most important reason which later made the Muslims in general & Omar Ben Al-Khattab particulary use the year of the prophet's migration from Mecca as the standard year for the Islamic calendar.
It is important for Muslims during praying to face, per God command, Kaaba in Mecca (Makkah) in Saudi Arabia; not to face Madinah (Medina).
To Madina..
Makkah
The first and most important holy city is Makkah (or Mecca) in the Kingdom of Saudi Arabia.
The holiest city for the Muslims is Makkah(Mecca),S.Arabia
Makkah, site of Masjid Al Haram, the site of the Kaaba. Medinah, site of the Prophet's Mosque, peace be upon him. Jerusalem, site of Masjid Al-Aqsa.
In Saudi Arabia's city Makkah.
Makkah and madina that is in saudi arabia
about 1000 km
Not generally
about 1350 km
Makkah. It is in Saudi Arabia