I've watched the Oversimplified Video and there was a bit about Wilmer McClean.

And the best part is, it was actually true!

Here let me copy and paste something from the internet

"The Battle of Bull Run, one of the first battles of the US Civil War, occurred on and around Wilmer McClean's farm in Northern Virginia. Not wanting to live surrounded by war, McClean and his family moved to Appomattox Courthouse, Virginia. The Battle of Appomattox Courthouse was the last significant battle between Union and Confederate forces. The Confederates signed the surrender order in Wilmer's sitting room. It is said that the Civil War started on Wilmer's farm and ended in his sitting room."