These topics relate to the 1800s, particularly post-Civil War, when the book Roll of Thunder, Hear My Cry is set.
Dred Scott Decision (1857) - Dred Scott was an African-American slave. He was taken by his master from the slave state of Missouri to the free states of Illinois and Wisconsin, then back to the slave state of Missouri. Scott sued for his freedom and the case went all the way to the Supreme Court.
Emancipation Proclamation (1863) - 1863 presidential decree from Lincoln. It did not actually "free all slaves" - it declared free slaves living in states NOT under Union control. It did allow black soldiers to fight for the Union and tied the issue of slavery directly to the war.
Reconstruction (1865-1877) The period right after the Civil War when the federal government set conditions that would allow the Southern states back into the Union.
14th Amendment to the U.S. Constitution (1868) - The Fourteenth Amendment granted citizenship to former slaves.
Sharecropping - After the Civil War, without land of their own, many blacks were drawn into schemes where they worked a portion of the land owned by whites for a share of the profit from the crops.
Post-Reconstruction Era (1877-early 1900s)