What year did phantom tollbooth win a Newbery Medal?

It did not ever win the award. It was published in 1961, so it would have been up for the 1962 awards. Here is the list from 1962:

1962 Medal Winner: The Bronze Bow by Elizabeth George Speare (Houghton)

Honor Books:

• Frontier Living by Edwin Tunis (World)
• The Golden Goblet by Eloise Jarvis McGraw (Coward)
• Belling The Tiger by Mary Stolz (Harper)

No Phantom Tollbooth. Sad.