If I do every state that I've stayed overnight in, I have 404:
If you added states that I've had day trips you can add 17 more (in blue):
Montana (shopping)
Idaho (shopping)
Wisconsin (Brewers game)
Driven through or had airport stops adds 41 more (in red):
South Dakota (stopped for lunch)
Nebraska (stopped for lunch)
Kansas (stopped for dinner)
Delaware (pure drive through)
Rhode Island (pure drive through)
Indiana (pure drive through)
Iowa (pure drive through)
Utah (airport stopover)
For a total of 475.