Pam, That first photo (from the UNLV Special Collections) may have captured the installation of the first Las Vegas Club sign, before they moved across the street later on.

I'm re-posting your picture here, for convenience:

Parked at the curb is a YESCO (Young Electric Sign Company) truck. Sign supports are on the building, a few doors south of the Monte Carlo.

Now, look at this Monte Carlo picture from the ChipGuide listing. This picture is looking south, down Fremont Street. And where the sign was being constructed, now there's a "Las Vegas Club" finished sign on the building.

(Yes, I'll admit to being a LV casino history nerd!)