Merlis asks, "What was the last non-stereo hit?" Or, where's the mono nucleus?

Bob Merlis, PR man, sent this e-mail to his friends and colleagues Tuesday:

Was just having a conversation with a friend and the Billboard Top 10 debut of John Mellencamp's No Better Than This album came up. 

Mentioned that it's John's tenth Top 10 album and that it's offered only in mono which begged the question: "What was the last mono-only album that debuted in Billboard's Top 10?" 

We're thinking it must have been over 40 years ago as albums were offered in both stereo and mono from the late 1950s onward.  Any suggestions? 

I'd love to make this a contest but since I don't know the actual answer, I'm not sure I'm in a position to declare a winner. Would love to hear your thoughts which I'd share with all the recipients of this inquiry.

Although I haven't asked him, I'm sure Bob would send a CD as a prize if the winning answer comes from KPCC. Leave your answers in the Comments section.

Meantime, when I read Bob's e-mail, the first thing I thought of was Ben Vaughn's album Mono USA, but I don't think it debuted in the Top 10, no matter how worthy. Ben appeared on Off-Ramp a couple years ago to talk about his album Designs in Music.

And of course, I always loved that song, Mono River, sung by Andy Williams.

(Smoking photo credit: Stephanie Pfriender Stylander)