Turns out it's one of three Douglas D-558 Skyrockets ever built. This one is #D-558-2 #1, and is on display at the Planes of Fame Museum, Chino, California.
Anonymous
@ 2009-01-09 12:38:29
That's actually a mock-up of the Bell X-2
Anonymous
@ 2016-10-07 10:37:54
it a mock-up of the X-2, it has the wrong tail for a d-558
No Longer There 
but the horizontal stabilizer is too high.