Willie Nelson wore the Astros sweater before Kate Upton was born

Willie Nelson sports the iconic Astros rainbow sweater in this photo taken in the late 1970s or early 1980s.

HOUSTON – Kate Upton may have made the Astros sweater famous, but there is photographic proof that a Texas treasure wore the throwback long before the supermodel was even born.

Yep! That's Willie Nelson proudly sporting the sweater in all its rainbow glory.

The photo can be found online in your standard Google search about the Astros sweater, but it took more digging by this KPRC 2 producer to find out the story behind it.

The man standing next to Willie is Herb Kelleher, founder and former CEO of Southwest Airlines. Kelleher was CEO from 1982 to 2001.

Willie autographed the picture for him. 

I contacted Southwest Airlines to find out the "when, where, what, why and how," because, inquiring minds want to know.

The airline's archivist said they can only date this photo to the late 1970s or early 1980s. They do not know where it was taken. They do not believe it was taken at an official Southwest Airlines event.

So, while there is still some mystery surrounding the photo, it's still pretty cool to see that the Astros were always on Willie's mind. (I had to do it.)

Willie is still doing shows so maybe he'll wear the sweater again when he's on the road again. (Yep. I did it again.)

As for the photo, I hope it's framed and sitting on Kelleher's desk somewhere.