Flatiron Lounge, a trailblazing bar that helped usher in the craft cocktail movement in New York, will shut its doors in early January after more than 15 years in business. An owner, Julie Reiner, said the reason for the closing is a rent increase on its West 19th Street space.

“The business model that we opened with 15 years ago no longer works with what the real estate’s worth,” Ms. Reiner said. “It’s a bar. There’s no door charge, there’s no bottle service, there’s no food. It’s a cocktail bar.” The rent is rising to more than $30,000 a month from $22,000, she said.

Flatiron Lounge was opened in May 2003 by a group of six partners, though Ms. Reiner, then a rising name in mixology, quickly emerged as the face of the business. Other Manhattan bars, notably Angel’s Share and Milk & Honey, had already taken a more serious approach to cocktails, using good spirits, fresh juice and precise measurements to fashion both classic and original drinks.

But those were tiny speakeasies. Flatiron, which was easy to find and could accommodate more than 160 drinkers, was the first New York bar to bring craft cocktails to a bigger audience, honing bar practices that efficiently delivered cocktails to large crowds without sacrificing quality.