Near the end of the Civil War, the Union was running out of room for new burials in plots in Washington DC and Alexandria.
So, looking to expand, they took over Robert E Lee's farm in Arlington for additional room, putting graves literally in his front yard. Lee was busy fighting (and losing) in central Virginia.
So some of the north's most hallowed ground was really established as a thumb in the face to R.E. Lee and his wife.
It was a very brutal war.