The seven churches had these characteristics contemporaneously, but taken in succession give us the history of the church on earth.
Chapter 2
Chapter 2:1-7—Ephesus — representing the church in its first days of spiritual declension, after departure of the apostles. Historically: to 167 A.D.
Chapter 2:8-11—Smyrna — The church persecuted in the days of the Roman Emperors Trajan and Diocletian. Historically: 167 to 313.
Chapter 2:12-17—Pergamos — The church becomes worldly and accepts the patronage of the Emperor Constantine. Historically: from 313 when the Edict of Milan freed the church from persecution until 606.
Chapter 2:18-29—Thyatira — The medieval church holding earthly and political power and persecuting the faithful followers of Christ. Putting the authority of "the Church" above the Word of God. Historically: from 606 when Gregory the Great asserted the supremacy of the Roman Bishop until 1529.
Chapter 3
Chapter 3:1-6—Sardis — Representing the Protestant Reformation after the ardor and devotedness to Christ and His Word had cooled off. The Reformation was definitely a work of God and He raised up such men as Martin Luther to bring to light from the Scriptures the truth of salvation which the Roman Church sought to suppress. Historically: 1529—the Diet of Spires made the Protest that gave the name "Protestant" to the movement.
Chapter 3:7-13—Philadelphia — A remnant gathered according to the Lord's own character of holiness and truth. They honor the Lord's Name and His Word and await His coming. They have only a "little strength" but the Lord commends them and owns them as His. Historically: from about 1820, continuing until the Lord comes (Rev. 3:88I know thy works: behold, I have set before thee an open door, and no man can shut it: for thou hast a little strength, and hast kept my word, and hast not denied my name. (Revelation 3:8)).
Chapter 3:14-22—Laodicea — The professing church in its last condition on earth before the Lord comes. It is so distasteful to the Lord that He spues it out of His mouth after calling for repentance. He is seen as outside and knocking for admittance. There is no improvement in the church, and this brings us to the end of "the things which are". Historically: perhaps from 1848, but certainly with us now.
Thyatira, Sardis, Philadelphia and Laodicea run concurrently until the Lord comes, after which Thyatira, Sardis and Laodicea merge, becoming part of Babylon the Great.