The wrecking ball hasn’t been kind to Minneapolis’ “Golden Mile,” a stretch of Park Avenue south of downtown where turn-of-the-century industrialists invested their lumber and milling fortunes in the construction of grand stone mansions.

In the late 1800s, escaping booming downtown development, wealthy citizens transformed Park into a quiet mansion district with wide boulevards, large lots and long setbacks. They paid to pave the road with asphalt — the first in the city — and taxed themselves to maintain the public greenery.

What local historians call “Minneapolis’ answer to Summit Avenue” has largely been demolished, drawing more attention to preserving the eight of 35 mansions still standing between Franklin Avenue and 28th Street. All of them now serve institutional uses and, notably, more than half have recently changed hands. The avenue itself long ago lost its residential character, following its 1940s conversion to a one-way street and subsequent widening to handle pre-freeway traffic.

Finding re-uses for the buildings is important for their long-term survival, but often requires alterations. Yet only two have historic designations protecting them against damaging exterior changes, which is why preservationists are designating two more.

“To me, you want to save the building,” said Susan Hunter-Weir, a member of the city’s heritage preservation commission who nominated two properties for designation. “How far do you have to go in allowing the … newer owners to make changes in order to save the building?”

The danger of leaving the buildings undesignated became clear for some Park Avenue enthusiasts recently when the 22nd Street home of George Peavey, son of grain elevator pioneer and Peavey Plaza namesake Frank Peavey, was converted from an at-risk-youth center to a mosque. The new owners tore out part of a 112-year-old veranda to build a cinderblock wheelchair ramp, and removed most of the detailed finishings inside — making even what’s left of the property difficult to legally protect.

“Hand-painted murals were just being chucked into a dumpster,” said Ryan Knoke, a local historian who conducted the research for the nominations. “And woodwork and hand-carved moldings and fireplace mantels, I mean just chucked.”

The leaders of the mosque could not be reached for comment. The city’s architectural historian, John Smoley, said this was possible because historic protections are only considered for non-designated buildings if they are going to be demolished. Designations typically only protect building exteriors.

“We’ve historically done a pretty good job of preserving mansions,” Smoley said via e-mail. “To such an extent that we have to remind ourselves to look beyond our wealthy, residential, white, milling-related heritage which, while certainly significant, represents only a portion of our community’s vibrant history.”

Next door, Yemmy Osonowo hopes to build medical offices serving people with mental illness inside the 1892 McKnight house, which was left in disrepair by a drug rehab facility that operated there previously. Built from red stone with two witch’s hat towers facing the street, the home’s first owner, Sumner T. McKnight, was a New York-born lumber magnate and real estate developer. It is now being studied for historic designation.

Ornate marble fireplaces still hint at the home’s heyday around the turn of the century, when it was the scene of large parties and social events. Its walls are supposedly insulated with more than 20,000 horse manes and tails, according to the AIA Guide to the Twin Cities — a local architecture bible.

It later became a speech and arts college before a nursing home moved in and built an addition in the 1960s. Osonowo bought the property in 2013 with plans to install offices and assisted-living space for people with mental health problems, but progress restoring it has been slow and expensive. He attributed it to unforeseen issues related to the age of the building.

“There’s a lot of work to be done,” said Osonowo, noting that the building needs new plumbing, electrical and sprinkler systems. A recent tour revealed glimpses of the past, such as a basement ballroom replete with a tiny side room for smoking.

Even bringing well-maintained Park Avenue mansions up to code can be daunting. The Zuhrah Shriners owned the Charles Harrington mansion on 26th Street, which is historically designated, for 82 years until St. Mary’s University bought it in 2011.

The interior remains well preserved, if a bit dusty, with intricate molding, murals and tile work gracing nearly every corner. But the historic portion of the home remains largely unused, since opening it for public access would require changes like installing an elevator.

“Since the Shriners had it since ’29, there were a lot of things that were grandfathered in as far as ADA compliance and such,” said Scott McMahon, St. Mary’s associate vice president for external affairs. “Once the property changed hands, those grandfathers no longer existed.”

Hunter-Weir is also trying to designate 2445 Park Av., a castle-looking gothic home designed by the architect behind City Hall and downtown’s Lumber Exchange building. It was built for Anson Brooks, whose lumber company’s operations extended from Florida to Oregon.

The mansion is still an office, after the departure of Lemna Technologies, but with new tenants: Midwest Home Health Care and a law firm.

Four years ago, People Incorporated moved a residential drug and mental health treatment center into a 1903 mansion built for the large family of Franklin Crosby, who followed in the milling footsteps of his prominent father, John, as an executive at what would become General Mills. A 2010 Finance and Commerce article says the property at 2120 Park Av. S., beside the McKnight mansion, was formerly an HIV/AIDS facility.

The other surviving mansions are the Swan Turnblad Mansion, now the American Swedish Institute; the second Anson Brooks mansion, now a funeral home; and the former home of the Cowles family, now an outpatient drug treatment center.

In all, only the Turnblad and Harrington mansions had local historic designations — Harrington’s is particularly rare since it also extends protections to the interior. The city’s preservation board approved designation for the Anson Brooks mansion earlier this month, with City Council signoff expected soon.

“I have been working diligently to try to get the remaining ones designated, if not the entire remaining stretch there of the former mansion district,” Knoke said.