Is "You Are My Sunshine" copyrighted?

I intend to use some of the lyrics from the song "You Are My Sunshine" for a short script I intend to write, but I could not find out whether the lyrics are copyrighted are not.

I was wondering if anyone might know? Thanks.
I know you can do a music search on ASCAP's website to see what's copyrighted and what's not. Maybe try to search on the SCL (Society of Composer & Lyricists) or shoot them an email. I'm sure they'd be happy to help.