CHICAGO (CBS) — It’s April 20, or 4-20, a sort of national holiday to celebrate marijuana.

The number can be traced back to a group of teens who met at 4:20 p.m. each day to get high.

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In this Original Report, Roseanne Tellez tells us how medical marijuana has given the day new meaning.

Once a hippie holiday to some, 4-20 is Patient Appreciation Day at a Mundelein marijuana dispensary where the mood was festive, and the waiting room was full.

“4-20 is a celebration,” said Ben Kovler, CEO The Clinic Mundelein. “It’s a time to be happy you have access to this kind of relief, and to feel better.”

Kovler said the date has drawn “record numbers” to the clinic.

After 20 years of pain, a woman said she has found relief and a new family at the clinic.

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“So now I have someplace to come where it’s accepted that I use an alternative form of medicine,” said patient, Heather Malewicki. “I’d like to celebrate it every day. 4-20 is just a day that I can kick it up a little more,” she laughed.

Patients packed the parking lot to take advantage of special deals to mark the date. Although some had no idea of the special meaning…

Karen Firnbach did not know the significance of 4-20 until this week. For her, any celebrating is based on the fact she has found relief in a substance she can buy legally.

“I’m terminal, you know, so the day’s a comin’,” Firnbach said. “It’s hard to fathom that. So yeah it helps immensely.”

Kovler, who sells everything from marijuana flowers, to patches and candies, is also celebrating an industry that’s grown from 3,000 to nearly 20,000 patients statewide.

So what is next?

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Kovler predicts better relief for patients, more jobs and a stronger industry; and as he put it, a continued tidal wave of new business.