Is a Comma Necessary in Spelling Out Locations?

Which sentence is correct?

1. She graduated from the University of California, Davis, in 2020.

2. She graduated from the University of California, Davis in 2020.

Similarly:

3. We visited their Arlington, Virginia, home.

4. We visited their Arlington, Virginia home.

According to Merriam-Webster‘s Guide to Punctuation and Style, #1 is correct, while #3 is preferred.

Addendum (11/28/2024): When it comes to commas, dates are similar to locations; a seemingly extra one helps to clarify. Here’s the guidance from the Wall Street Journal stylebook:

Incorrect:
May 14, 1932 was his date of birth.

Correct:
May 14, 1932, was his date of birth.

Incorrect:
May 1932, was the start.

Correct:
May 1932 was the start.