Walker's intention was to remind readers of racism in this country, and that the racism has a base in history. If we forget the history, we are doomed to repeat it. The history comes in the mention of the sharecropper's cabin and the dead body. Sharecropping was prevalent after the Civil War. It is an agricultural system in which a family would farm a certain part of land and share the crops/profits with the owner of the land. Many claim that it was an economic way to keep the freed slaves in servitude. At its heart, sharecropping was similar to indentured servitude.
In addition to this allusion to African-American discrimination, the body found by the girl has clearly been lynched. Lynching was a far too accepted practice in post-Civil War America. It was a vicious example of the discriminatory acts of whites against blacks.
The young girl in this story is happy, enjoying the summer, innocent. However, in stumbling upon the dead body, she and the readers are forced to see that not everything is so good. No matter how much "better" it seems, racism is still too prevalent in this country.