When Peter proclaims to Jesus, “Thou art the Christ, the Son of the living God,” Jesus replies that on the basis of His being both Christ and God’s Son, He will build his church (Matt. 16:16, 18).
Then, in Acts chapter 2, when the Gospel is preached for the first time and the first converts are saved, the Lord begins adding those who are being saved to the church (vss. 42-47).
That is where the church of Christ began.
Jesus is the Christ. Jesus Christ built a church. Therefore, the church that Jesus Christ built is the church of Christ. That’s not the name of it—that just shows Who it belongs to.
In the New Testament, after Acts 2, the church exists in two forms: universally and locally. Jesus only built one church, but in the New Testament there are congregations of that church in Jerusalem, Antioch, Thessalonica, Ephesus, Corinth, and lots of other places.
But unlike modern practice, people do not “join” the church of Christ. The practice in Acts 2 is still binding today. When sinners hear, believe and obey the Gospel, they are saved as the Lord adds them to His church.
The Apostle Paul established many of the congregations of the church of Christ that you read about in the New Testament. None of them were in Jerusalem, where the church began, yet they were just as much the church of Christ as the congregation in the Jewish capital.
When Paul ends his letter to the church of Christ at Rome, he says, “The churches of Christ salute you” (Rom. 16:16). He is sending greetings from other congregations of the Lord’s church to the congregation of Christ’s church at Rome.
Today, people ask, “What church do you attend?” Or, “Which denomination do you go to?” But that question is never asked in the New Testament, because in the first century, when the Apostles took the Gospel to the world, there was only one church.
The church of Christ is not a denomination. It’s the body of Christ (Col. 1:18), the church Jesus purchased with His blood (Acts 20:28), the church He died for (Eph. 5:25), the church he saves (Eph. 5:23). That church still exists today all over the world.