Arlington isn’t actually located in Washington, DC, but just outside it, in Virginia. That’s because the land was seized from Robert E. Lee’s plantation in 1864. There were other options for the location of a National Cemetery, but the government specifically wanted to bury Union soldiers on Lee’s land as an insult to the Confederate general. Brig. Gen. Montgomery C. Meigs wanted to make sure the place was uninhabitable if the Lees ever tried to return. He ordered the graves placed as close to the mansion as possible.
After the war, the Lees owed about $1,400 in today’s money in taxes on the estate. Mrs. Lee sent someone to pay the tax, but the government refused to accept it. Instead they took half the land in a public auction and ordered the establishment of a National Cemetery.
But then Lee's grandson sued to get the property back. Read the rest of that story and others at mental_floss. Link