What is the main theme in "uncle john's farm" by mark twain?

The main theme in "Uncle John's Farm" by Mark Twain is about his childhood memories on his Uncle John Quarles’s farm. Mark describes the time he spent on the farm, especially the summers where he witnessed the practice of slavery and talk about his feelings towards it, and how they impacted on him.  

3 is blunder, i’m not sure about the last one but the first two look correct

in the 1890s, southern states enacted a new form of black codes, called “jim crow” laws. these laws made it illegal for blacks and whites to share public facilities. this meant that blacks and whites had to use separate schools, hospitals, libraries, restaurants, hotels, bathrooms, and drinking fountains.

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