One Church - One City
Although the oneness of the local assembly as related to a particular city is generally ignored or unknown in christendom, the following study of the scriptures would convince any serious inquirer of its importance.  That it cannot be worked out fully because of the divided state of the public church is no excuse for not acknowledging and acting on the principle as far as possible.

The Practice Among The Brethren

One Church - One City ... Truth or Practice?

A review of the Acts of the Apostles and of Paul's epistles will show that the New Testament links a particular church with a particular city when referring to churches locally:

1)   In referring to a city - the church in Ephesus, the church in Smyrna, the church in Pergamus, the church in Thyatira, the church in Sardos, the church in Philadelphia, the church in Laodicea [Revelation 2-3] - the singular 'church' or 'assembly' is always used.  The church in Jerusalem, the church in Philippi, the church in Corinth, the church in Antioch, the church in Cenchrea are other examples of assemblies specifically identified with the city in which they resided.

2)   In referring to a region or province - Judea, Galatia etc. - the plural 'churches' or 'assemblies' is always used, implying that regions or provinces had many assemblies most likely recognized city by city.

3)   References to “the church in so and so's house” [Romans 16:5; 1 Corinthians 16:19; Colossians 4:15; Philemon2] can easily be shown to coincide with a particular assembly in a particular city.

This can be confirmed using any concordance.

One church in one city did not restrict the number of gatherings within the church identified with that city.  

1)  There were many believers in Jerusalem after Pentecost and the churches inception - "the number of the men had become about five thousand.”  [Acts 4:4]   Acts eventually addresses the church in Jerusalem [Acts 11:22].

2)   Also in Jerusalem, Peter "came to the house of Mary, mother of John, where many gathered together and were praying … And he went out and went to another place." [Acts 12:12-18]

3)   At Corinth the Lord tells Paul "I have many people in this city."  [Acts 18: 10]   Evidently they came "together in assembly,"  [1 Corinthians 11:17] - probably in smaller groups.  But for edification Paul says, "If therefore the whole assembly comes together in one place," [1 Corinthians 14:23] showing that attempts were made to join all the saints in that locality in one place.

4)   Paul addressed himself "to all that are in Rome,”  [Romans 1:7] although taking account of several gatherings in that city.  [Romans 16: 3-15]

5)  Paul exhorted the elders in the church in Ephesus to care for "all the flock" - not a part of it - in that city, implying that there were many gatherings of saints, not just one.

6)   James was an elder in the church in Jerusalem.  He told Paul that there were tens of thousands of believers in that locality. [Acts 21:20]  Linking this thought with Acts 2:46, saints gathered from house to house and were still considered part of the church in Jerusalem although they did not all meet in one place at the same time.

 From the above it can be fairly deduced that no matter how many gatherings there were in a city, the New Testament writers condoned only one assembly or church identity in a particular city while including all the saints in that locality.

In addition, Paul's teaching as to one body in Romans 12 and 1 Corinthians 12 also bears on this matter, not allowing for any independency of Christian groups or organization.

Although the unity of the local assembly is generally ignored or unknown in christendom, the above scriptures would convince any serious inquirer of its importance.  That it cannot be worked out fully because of the divided state of the public church is no excuse for not acknowledging and acting on the principle as far as possible.

See also:

The Practice Among The Brethren

One Church - One City ... Truth or Practice?