The Campbell Mithun advertising agency, a downtown Minneapolis fixture since 1933, is moving into the historic 510 Marquette building, the core of which was designed by renowned architect Cass Gilbert and was once home to the Minneapolis Federal Reserve.

The agency will serve as anchor tenant in the 13-story building and occupy 65,000 square feet of space on the top four floors plus a penthouse structure on the rooftop.

Campbell Mithun, which will leave its namesake building, the Campbell Mithun Tower, at 222 S. 9th St., intends to occupy the new space in late 2014, the agency is scheduled to announce Monday.

“We’re moving now because the climate is right and after taking stock of what we can do to be part of the energy of the city,” said Campbell Mithun CEO Rob Buchner. “We made the decision with an eye on the future and the next generation of creative people.”

The move brings the 250-employee firm into the revitalized area of downtown Minneapolis and puts it at a key light rail station. The new location is adjacent to the recently completed Soo Line luxury apartment tower, the under-construction Nic on Fifth apartment high-rise and the new headquarters of Xcel Energy.

The building is being developed by Ned Abdul of Swervo Development Corp., which purchased the structure for $6.7 million earlier this year. The exterior will also be refurbished.

The floors on which Campbell Mithun will reside have been stripped down to the original brick facade and will keep that feature as Julie Snow Architects designs the agency’s new space. Julie Snow Architects also was recently selected to be part of the Nicollet Mall redesign team by New York-based James Corner Field Operations.

Buchner said the new space will more conducive to collaboration and flexibility than the old space and will include room for growth. Campbell Mithun occupies 80,000 square feet in its current location.

“What’s nice about this space, as opposed to [the Warehouse District] is that it’s never been a tool-and-die company and doesn’t have that distressed look. The floors were designed for white-collar workers,” Buchner said.

Buchner acknowledged that there will be a cost savings in terms of Campbell Mithun’s lease in the new building but that those savings will be redirected into new capabilities for the agency, including high-tech data analytics.

The building was originally constructed in 1921 for the Federal Reserve. Gilbert, the architect, also designed the Minnesota State Capitol. The tower into which Campbell Mithun is moving was built later.

Campbell Mithun’s occupancy of space that includes the 13th floor fits with the legacy of agency founder Ray Mithun, whose first office was on the 13th floor of the old Northwestern Bank building and who considered 13 a lucky number.

Campbell Mithun is one of the legacy ad agencies in the Twin Cities with clients that include General Mills, Land O’Lakes, Popeyes and Chipotle. It also has its media planning and buying division Compass Point Media.

“This moves takes us to a different part of the city and a different environment,” Buchner said. “Change is good for any organization that wants to stay competitive. It’s a symbol of our commitment to the future.”