New York’s first state-licensed pot shop found itself in the green Thursday, serving as many as 500 customers in just a few hours as weed lovers flocked to the grand opening in Manhattan.

A massive line of eager stoners — some already smoking — waited in a massive, blocks-long line to make their first legal marijuana purchases at the Housing Works Cannabis Co. store 750 Broadway in NoHo, which fittingly opened at 4:20 p.m. sharp on Thursday.

The crowds were so large that the dispensary had to turn away hundreds of other customers by the time they closed just after 7 p.m. — even those who had been waiting for four hours.

Despite the immense volume, the store’s assistant manager was high on the success of the opening day.

“If you were a part of the community you definitely wanted to be here today,” assistant manager Britt Buchner told The Post shortly after they’d shut their doors to more customers. “It was absolutely what we expected and then some but we were able to control the energy, which was very positive.”

Buchner estimated that they served close to 500 people with all kinds of marijuana products — from pre-rolled joints to THC vape cartridges to gummy edibles. About 150 others were turned away and asked to return on Friday, The Post observed.

The store, which remains the only shop in New York with a state license to sell cannabis, anticipated the major crowds and expects the volume to remain at that extreme level for the next few weeks. Buchner noted that as the first marijuana store to open, they have no model to follow.

“We made sure we had proper security measures in place, made sure we had some ropes to keep the line in control. We also had members of our staff going out to the line and talking to folks throughout the evening,” Buchner said. She said the store currently has 14 people on staff, but expects that number to grow.

While buying weed on the street may be cheaper than $40-$60 for an eighth of an ounce offered by the shop, Buchner said the customers were elated to be able to purchase products that have been tested.

“It was like a bunch of kids on Christmas,” she said. “It was great to be met with all the smiling faces and energy and excitement. Everyone’s excited that these are all New York brands — they’re small farmers they’d never heard of. They’re excited to try them and give us their feedback.”

“The biggest thing we want to emphasize is the safe consumption you get with us. Everything here has been tested and you know what you’re getting in your products,” she said.

The business is cash-only.

Cesar Soriano, 33, of Park Slope in Brooklyn, was exactly the type of customer Buchner was talking about. He braved the line to be part of what he considered a historic moment.

“I can get better weed from other places but it’s not about that for me, it’s about the milestone New York has reached. I’ve come to show support for the first legal dispensary, given I’ve been selling cannabis for years before it was legal,” Soriano said

“The dispensary will work for people who want to go somewhere where they feel comfortable without doing any sketchy transactions on the corner,” he continued. “Bodegas don’t guarantee quality, cleanliness and the stuff’s not tested. Unless you’ve got a trained cannabis palate, you don’t know if you’re getting the strain you asked for.”

Alex Tractenberg, 22, of Greenwich Village, said he paid someone $50 to wait for four hours so he could go straight to the front of the line. He picked up some edibles and a vape cartridge and was heading to go watch Avatar 2.

“It’s nice to have legal weed that’s regulated and you know it’s going to be good,” he said.

“It was kind of like a club in there. They a DJ and people walking around with drinks and snacks,” he continued. “I’ve had bad experiences with products at bodegas. I know it’s safe here and it’s good stuff.”

Meanwhile, West Village resident Amy Wachtel — who does not smoke — hopped on line at 3 p.m. to buy weed gummies and a pre-rolled joint for her boyfriend, but was disappointed to learn she was probably not going to be able to make the purchase today.

“They’re letting us down easy, giving us the impression we probably won’t get in. But after four hours we’re not taking no for an answer,” she said.

Wachtel said it seemed the store was more successful than they expected “and less organized than I would have hoped.”

“It would be nice if they gave us an extra gummy or pre-roll as a show of good faith,” she said.