The milestone seemed unreachable just three years ago and comes as Tesla has seen a string of profitable quarters and a buoyant stock.
As Tesla completes a factory in Berlin, Mercedes-Benz and Audi are introducing electric cars in bids to defend their dominance of the luxury market.
The electric-car maker will be the biggest addition in the history of the benchmark index. Will that settle down its swings?
Mr. Musk said on Tuesday that he had moved to be near a new factory Tesla is building outside Austin.