Groupon on Monday unveiled a long-awaited daily deal that's sure to sell out not long after its debut: Vastly-discounted Chicago Transit Authority three-day passes.

The deal offers up three-day, unlimited-rides CTA passes for a mere $9 -- that's 36 percent cheaper than their usual $14 price tag.

The Chicago Tribune previously reported that Groupon purchased 250,000 passes for the deal at a wholesale rate of just $7.53 each, a deal worth $1.88 million for the cash-strapped agency. The deal marks the first partnership between Groupon and an American transit company.

As of mid-Monday, with five days left to go, over 5,000 have been apparently wooed by the Chicago-based site's romantic description of Chicago's principal public transit system:

Growling engines, beeping horns, and clattering train wheels are indelible sounds of Chicago's streets. And every day, more than one million travelers hear this din from inside the Chicago Transit Authority's buses and trains.

A maximum of four passes may be procured per person.

Photo by vxla via Flickr.