My Texas Girl is a western song recorded by the Carters in 1935. It appears the song is a rewrite of one of the "Sleepy Rio Grande" songs. According to Tex Rhinehart "Sleepy Rio Grande" is a mondegreen for "Silvery Rio Grande" so it's possible the song was "Silvery Rio Grande" at some point.

Bob Miller's 1934 songbook had the song "Sleepy Rio grande." Other titles include: "Where the Sleepy Rio's Flowing," and "By the Sleepy Rio Grande."

I'd bet the Carters song is based on the Carson Robison, Frank Luther song "Sleepy Rio Grande" backed by "When it's springtime in the Rockies" which was a huge hit for Victor in 1929. They recorded songs under the alias "Bud and Joe Billings"

Anyone have the lyrics?

MY TEXAS GIRL-Carter Family

All my life I've wondered if what I done was wrong
All I ever cared to do was ride my pony on
I never had no heartache was always happy and gay
Until I met a Texas girl who stole my heart away.

CHORUS: Where the sleepy Rio Grande goes slowly to the sea
It was there she promised to be mine throughout eternity
But the angels they grew jealous of her beauty and her smile
And came along one stormy night and stole away my bride
The birds have hushed their singing sadness is over the land
The birds miss my darling by the sleepy Rio Grande

Her lips were like the Russian wine her hair it hung in curls
Her cheeks were like the dawn of day that breaks upon the world
She's gone and left me lonely I miss the touch of her hand
Tonight while I am walking by the sleepy Rio Grande