Walnut Brewery, a longtime fixture in downtown Boulder, will close June 4, to be replaced by another staple of the city: Boulder Beer.

Tennessee-based CraftWorks Restaurants & Brewery Group, the current owners of Walnut Brewery, announced Thursday a transfer of ownership to Boulder’s Frank Day, founder of the original Old Chicago in Boulder and owner of the Boulderado Hotel. Day’s wife, Gina, is a part-owner of Boulder Beer, which will open Boulder Beer on Walnut in July.

“We’re Colorado’s first craft brewery, and there’s no better way to grow our legacy than to take over the location of Boulder’s first brewpub,” said Jeff Brown, Boulder Beer’s president and partner. “I’m really excited to have the opportunity to work with Frank and expand downtown.”

Brown has worked with Frank Day before: He was on the opening team of the Walnut Brewery, which debuted in 1990 at 1123 Walnut. The brewpub inspired Day to eventually launch Rock Bottom Restaurants, which grew into a 141-chain, $382 million group that included the Rock Bottom, Old Chicago and ChopHouse brands.

Day sold the business in 2010 for an undisclosed amount to a New York private equity firm, Centerbridge Capital Partners. Centerbridge purchased Gordein Biersch Brewery Restaurant Group at the same time, folding both enterprises under the CraftWorks heading.

Day approached CraftWorks “a few years ago” to see if they’d be interested in selling it back to him. He felt the company hadn’t done enough to energize the place, “one of his favorites, if not the favorite, I’ve ever done.”

He and Brown don’t plan to change much. Walnut’s much-loved brews will still be available on tap, and Boulder Beer will use the location to concoct smaller-batch, specialty beers in addition to its traditional offerings. But Day did feel it necessary to re-brand the brewery under the Boulder Beer heading.

“The whole world of craft beer is getting extremely competitive. ” he said. “We’ve got a better situation with them together than either just alone. We think it’s a 2 + 2 = 5 deal.”

The number of brewpubs in the U.S. has been steadily growing since at least 2012, according to Boulder-based Brewers Association. There were 1,916 brewpubs in 2016, up 10.8 percent from the prior year.

Boulder Beer is the second long-time local brewery to make moves into Boulder’s downtown recently. Longmont’s Oskar Blues last month announced it would open a taproom at 921 Pearl St. later this summer. Boulder Beer on Walnut is aiming for a post-July 4 opening, Day said.

Shay Castle: 303-473-1626, castles@dailycamera.com or twitter.com/shayshinecastle