Streetscapes: How old is old enough for a building to be labeled historic?

Historic preservation is typically associated with buildings that have been standing for a century or longer. But should the same protections extend to 50-year-old buildings that were erected during an era of suburban flight and urban renewal?

It's a hot topic these days in historic preservation circles. Turning 50 makes it easier to list buildings on the National Register of Historic Places, even if the angular designs and exposed concrete of the 1950s and '60s don't inspire the same nostalgia as their 19th-century counterparts.

Not all buildings from the era are significant, but determining which ones qualify requires research that today remains sparse. A listing itself does not protect a building in most cases, but cities like Minneapolis apply extra scrutiny to properties on the register if the owner wants to demolish them.

"Preservation is a difficult argument to make to begin with," said Todd Grover, who heads the local chapter of Docomomo, a group dedicated to documenting and conserving "modern movement" architecture. "And when you add this modernism on top of that it makes it even more difficult. That's why there needs to be more information, more understanding and more awareness."

The latest front in this debate locally is in Minneapolis' Dinkytown district, where the 1963 Ralph Rapson-designed Southeast library is under threat. Hennepin County is assessing what to do with the building, whose small size, blind spots and rigid design make it difficult to operate as a modern library.

Some are eyeing demolition, but that is likely to draw fierce opposition from preservationists like Grover, whose group is bringing its annual national symposium to the Twin Cities this year.

"This is a prime property that unfortunately is an unbelievable example of Ralph's work," Grover said of Rapson, Minnesota's most prominent Modern architect and a longtime head of the University of Minnesota's architecture school.

Rapson designed the first Guthrie Theater, enveloped in distinctive wooden frames, also in 1963. A Save the Guthrie movement coalesced in the early 2000s to save the building because of its architectural and cultural significance, but the City Council ultimately overturned the city's heritage preservation commission and allowed demolition to proceed in 2006.

Built as a credit union, Rapson's Brutalist library features a coffered roof deck that extends over cruciform concrete columns to a surrounding plaza.

"A lot of Rapson stuff has been torn down in the last few years," said Elizabeth Gales, president of Preserve Minneapolis, a volunteer preservation group. "So that kind of makes Southeast Library pretty important. And I know that it has accessibility issues, but frankly, a ramp and elevators — things could be done."

A 2013 assessment concluded that renovation was feasible, though the building's shortcomings as a library space would be hard to overcome. "It needs an enormous amount of money to get it up to decent shape," said County Commissioner Peter McLaughlin, "to the point where I don't think it's worth it to do that."

McLaughlin said demolition was a "possible outcome," though Hennepin County Library's capital projects manager Lois Lenroot-Ernt was hesitant to say it was a serious option until there has been more community engagement. Alternatively, the library could move and the building potentially find a new use.

Even the most unloved properties from that era can be saved, if someone proves they are significant. Take the 1975 Peavey Plaza on Nicollet Mall, which the city had planned to demolish to make way for a more accessible and inviting space.

Two groups sued to save it, highlighting it as a formative work of architect M. Paul Friedberg. They also listed it on the National Register of Historic Places, a big feat for a property less than 50 years old. The city eventually backed down and now plans to rehab it.

Rapson's 1973 Cedar Square West complex, known for its multicolored panels, also was added to the National Register of Historic Places in 2010. The project, now called Riverside Plaza, was highlighted for being the first urban example of a federal program geared toward creating planned communities.

"Whether … you love or hate Cedar Square West or Riverside Plaza, it's important and it changed the landscape," said Gales, who helped get the property listed.

Suggestions of saving other buildings from that era are sure to raise eyebrows, however. Grover pointed to the shuttered Macy's in downtown St. Paul, a 1963 windowless former Dayton's department store building designed by Victor Gruen, the same architect behind Edina's Southdale.

"Around the same time as Southdale, [Gruen] did a downtown store very similar to what was happening in the suburbs," Grover said. "Granted it [has] been modified quite a bit inside over time, but I think the bones of it are still there and the concept is still there."

The Macy's property — now owned by the St. Paul Port Authority for possible redevelopment — is among a number of buildings earmarked for a St. Paul "urban renewal district" studied during the Green Line light-rail planning. Minneapolis has also explored the possibility of a similar Gateway historic district, designating some of the imposing boxes that replaced the tiny storefronts of its skid row.

"We're taking a look at some of those more recent properties and saying, 'Hey, not everyone may have been thrilled with what happened back then, but that was a definite historical movement that was significant not just here in Minneapolis but across the nation,' " said John Smoley, architectural historian for the city of Minneapolis.

A survey done several years ago identified more than 100 post-World War II properties around Minneapolis that may be historic. In addition to the Southeast library, prominent buildings include the Hennepin County Government Center, the now-demolished Metrodome, the City of Lakes building and Xcel Energy's Nicollet Mall headquarters.

Another prominent structure in that class — the 1956 Lutheran Brotherhood and Minnegasco building on 7th Street in Minneapolis, known for its green curtain wall — is gone. It was the first significant new downtown office building since the 1930s when it was built, according to the book "Lost Minnesota: Stories of Vanished Places."

Minneapolis and St. Paul destroyed so many great structures during their postwar decline that proposals to save their successors are likely to draw ample public skepticism. But urban renewal's disregard for now-beloved 19th-century buildings illustrated that architectural tastes change dramatically over time. It's a good reason to occasionally put "beauty" aside and take stock of what is significant, since we might miss it when it is gone.

Eric Roper • 612-673-1732

Twitter: @StribRoper