The dirty history of the "No Trespassing" sign

The "No Trespass" law was originally instituted to maintain control of Black southerners  during  the post-Civil War era. It was included among the most vile of slave codes used by Confederate states to hold power after the 14th Amendment was passed in 1865, which granted citizenship and equal protection of African-Americans under the law. 

Before the Civil War, there was no documentation of any trespass laws. The American countryside had unrestricted access, and slaves were known to live off the land they resided on. It wasn't until 1865, when southern states started implementing the "No Trespass" statute along with other post-antebellum Jim Crow laws, that property owners aggressively enforced their right to protect their property. Often plantation owners would use the trespass law to drive off freed slaves who lived off their land, or to keep their former slaves confined to their property.

The "No Trespassing" sign has prevailed over decades because of its broad nature. It was never specifically recognized as a slave code because it applied to everyone; nonetheless, its intended use was meant for Black Americans and disproportionately enforced towards them. Northern states eventually adopted the law because they liked the idea of privatizing the countryside. Large landowners also often had more political power. Employers also liked the law since it prevented distraction employees would get from outdoor pastimes.