Colorado-Based Manufacturers

Here ya go!
 http://americanmadeaudio.com/product-tag/colorado/

Coors

 Green Mountain Audio, Colorado Springs, is not on the list Yogyboy provided..

Zenwave Audio

PranaFidelity is in Denver.  

Sanders is in Conifer

Audio Magic cables and YG Acoustics are all I can think of. But jetter nailed the biggest seller👍And oldest company and probably the Best audio tweek. Of course it goes with other enhancements available In Colorado 

I believe Jeff Rowland is Colorado based.

MG Audio design

Galibier Design turntables are made by Thom Mackris near Boulder.
Grand Prix turntables and racks are made in Durango by Alvin Lloyd and crew.
Westone IEMs are made in Colorado Springs, as are Jeff Rowland's products.

Cal3713, what's up with this? Just idle curiosity, or---?

Bill Leebens, Director of Communications, PS Audio

@itsleebs, etc.  Thanks folks. As for why, it's time for a career change and trying to investigate companies I might be interested in working for. 

Boulder. Duh!

Starbuds. 12 locations. 😳

Another one missing from Americanmadeaudio.com is Grace Audio

Pro stuff based in Lyons, north of Longmont/Boulder.

Isn't Durand, the tonearm manufacturer, also in Colorado?

I can't believe no one mentioned the Avalon Speakers...

Avalon in the OP and the link above!

Lol, why the list?

Isn’t Durand, the tonearm manufacturer, also in Colorado?

Joel is out of Seattle. I helped him with the launch of the Talea back in 2010/2011, so that might be the source of confusion about a Colorado connection.

... Thom @ Galibier Design

50 years ago most audio manufacturers worked out of Long Island City ,N.Y. NEW YORK ,NEW YORK.....