Historically, people have built fences, mainly, to keep other people out of their stuff, or out of their beliefs.

Here are some fence-building notations, all of which have some sort of anniversary today, June 12th.
• In 1838, the Iowa Territory was organized.
• And in 1963, Civil rights activist Medgar Evers was fatally shot in front of his home in Jackson, Mississippi.
• On this date in 1929, Anne Frank was born. She was killed some 15 years later.
• 2008, a deeply divided Supreme Court ruled that foreign detainees held for years at Guantanamo Bay in Cuba had the right to appeal to U.S. civilian courts to challenge their indefinite imprisonment without charges.
There are lots more. Way more.