You haven't missed anything.I've never been any where near the grassy knoll.
It's a patch of grass on the side of a narrow freeway entrance.
If it didn't have history tied to it,
it would have probably been obliterated many years ago to widen the on ramp.
The odd thing about that area is the city choose to use the island of land in between the roads going into downtown and out as the place for the memorial.
The "grassy knoll" is across the street on the same side as the SBD which has been turned into a morbid museum.
I've never been to the Ford's Theater in Washington, D.C.