Marijuana has long been an illicit yet integral part of the annual Lollapalooza music festival in Chicago. This year, it’s legal for the first time in the event’s 30-year history, and potentially big business.

The four-day event began Thursday in Grant Park, and nearby Chicago cannabis dispensaries are stocking up and staffing up for what they hope will be a major sales boost.

The Sunnyside dispensary on North Clark Street in River North — the closest marijuana shop to Grant Park — has brought in corporate support staff, extra product and charted out logistics to handle a boisterous influx of Lolla attendees looking for a legal buzz during the festival.

“We expect it to be our busiest weekend that we’ve had to date since we opened, and are prepared to handle it. The store is fully staffed — it will be the first time we will have all 12 registers open,” said Jason Erkes, a spokesman for Chicago-based Cresco Labs, the large multistate cannabis operator that owns the dispensary.

Lollapalooza was canceled last summer during the height of the COVID-19 pandemic. It returns as the delta variant spurs a rise in case counts and new mask guidelines from health officials, but attendance is expected to be robust.

As the festival began Thursday, Cook County was not yet on the list of places where masks are recommended indoors for vaccinated people. The dispensaries are staying vigilant, but for now, masking is mostly a suggestion for unvaccinated customers.

“Right now, if you’re vaccinated, you can shop without a mask,” Abigail Watkins, spokeswoman for Dispensary 33 in the West Loop, said Wednesday. “If there’s a new mask mandate, obviously we will have to change our policy.”

Its River North location will be fully staffed through Sunday, and Sunnyside has brought in backup staff from other stores and its corporate office to help with order-taking outside the store, Erkes said. Budtenders will be highlighting an express menu to expedite the process.

Dispensary 33, which launched Chicago’s first medical dispensary nearly six years ago on North Clark Street in the Uptown neighborhood, opened its first recreational dispensary in May on Randolph Street in the West Loop after a protracted zoning and licensing dispute over a proposed NuEra dispensary across the street.

Bryan Zises, a principal with Dispensary 33, said he lost the zoning battle “at every turn,” but ended up opening the Randolph Street dispensary first, and remains the only recreational cannabis store in the trendy neighborhood.

At Ascend by MOCA on West Ohio Street in River North, the dispensary has stocked up on bestselling items including prerolls, chillums, vapes, flower and edibles, as these products are “most fitting for the concert experience,” said Chris Melillo, chief revenue officer for Ascend Wellness Holdings, a New York-based multistate cannabis company that owns the dispensary.

The dispensary expects its proximity to Grant Park to make for one of the most successful sales weekends to date, Melillo said.

One issue may be whether the cannabis products are actually allowed on festival grounds.

The Lollapalooza website does not list any marijuana products as prohibited, but does note that smoking and vaping are not allowed by the Chicago Park District.

C3 Presents, the Austin, Texas-based company that produces Lollapalooza, did not respond to a request for comment Wednesday about marijuana usage at the festival.

A Park District spokeswoman did not respond to a request for comment.

If history is a guide, weed will likely find its way into the festival.

“I can’t speak to what the rules for Lolla are specifically,” Sunnyside’s Erkes said. “But I can tell you that cannabis and music festivals go as far back as Woodstock over 50 years ago. And I wouldn’t expect that this year’s Lolla will be any different.”