What was the makeup of the church in Corinth?

The church in Corinth was not a large congregation. It consisted of a good cross-section of the society of Corinth who had become believers. Paul addressed them as believers who had been designated the wisdom of God, though he rebuked them for lacking a wise man among them.

Les explains that the church in Corinth was not huge, but it had a pretty good cross-section of the society of Corinth who had become believers. Paul says there was not a wise man among them, and he speaks to their shame. He reminds them they are all believers and have been designated the wisdom of God. So the makeup was socially diverse but not large, and they were believers.

1 Corinthians 6:5

I speak to your shame. Is it so, that there is not a wise man among you? no, not one that shall be able to judge between his brethren?

What was the church in Corinth like when Paul wrote 1 Corinthians?

When Paul wrote 1 Corinthians, the church in Corinth was not huge but drew a cross-section of Corinthian society who had become believers. Paul said there was not a wise man among them, though they had been given God's wisdom. They faced judgments about this life and were told to appoint the least esteemed to judge.