The printing press was invented by J. Gutenberg around 1439. It was a dramatic improvement in printing mechanisms, and it allowed for the first time in history the mecanized generation of multiplies copies of a written text. Previously, such works were done by hand and only one copy at the same time, and were mostly performed by monks.
The global spread of the priting press was a total revolution. It enabled to transmit written pieces of work very fast. In Europe, during the Reinaissance, it set the starting point of the era of mass communications, which has permanently, since then, triggered transformations in the structures of the societies. For example, revolutions emerged because the quick and unrestricted transmission of the revoutionary ideas occurred thanks to the existence of the printing press.
After the American Civil War in 1865, where 4 million slaves got their freedom and for the first time they were able to enjoy liberty of speech and movement, education for their children, the right of a fair trial as well as all the privileges of American citizenship, a reconstruction period took place.
In such reconstruction period, Congress acted to prevent Southerners from going back to the white supremacy, by placing federal troops to protect the rights of black citizens. But when reconstruction ended in 1877 federal troops were withdrawn and thus white supremacy returned to the old Confederate states. Consequently, black voting fell off because of threats mostly by white employers and the secret organization determined on preserving white supremacy known as Ku Klux Klan.
The answer is the right to life, liberty, or property!