What was the first documented history of the Church?

That would be when God inspired Moses to begin writing down [documenting] it:

"This is he [Moses], that was in THE CHURCH in the wilderness with the angel which spake unto him in the Mount Sina, and with our fathers: who received the Lively Oracles [documentation] TO GIVE TO US." (Acts 7:38 KJV)

Same verse [NLT] New Living Translation: "Moses was with the assembly of God's people in the wilderness. He was the mediator between the people of Israel and the angel who gave him Life-Giving Words[documentation] on Mount Sinai to PASS ON TO US."