What is the main theme in "Uncle John's Farm" by Mark Twain?

In "Uncle John's Farm", an essay by Mark Twain, he vividly describes his experiences as a young boy on his Uncle John A. Quarles' farm near the town of Florida, Mo. Twain spent a few months a year there for several years until he was about 12. It was there Twain met the slave known as Uncle Dan'l, who became the model for the great character Jim in "Adventures of Huckleberry Finn."

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