A map of the Seven Churches of Asia Minor. Ignatius wrote letters (available on this site) to most of these churches. Asia Minor is now modern day Turkey and also the birthplace of the first churches of Christianity. Ignatius corresponded with these churches to keep them thriving in a time of persecution and strife. Asia Minor was conquered by Rome in the 2nd Century BCE and enjoyed a long period of peace until the Middle Ages.
The seven churches in Asia Minor are symbolic in themselves. The Biblical book of Revelation speaks of the seven candlesticks that undoubtedly represent the seven churches of Asia Minor. "The mystery of the seven stars which thou sawest in my right hand, and the seven golden candlesticks. The seven stars are the angels of the seven churches, and the seven candlesticks which thou sawest are the seven churches" (1:7). Various historical and religious figures came from Asia Minor, including Polycarp of Smyrna, one of Ignatius' closest friends.