For much of the 20th century, private developers ignored Harlem, deterred by its high crime rate, profusion of subsidized housing, and long trek from Midtown. During the malaise of the 1970s, the city owned well over half of the real estate in this storied neighborhood, long regarded as the nation’s black cultural capital.

Then, in the past decade, everything changed. As property values in other Manhattan districts soared, Harlem became the new development frontier. City leaders helped spur the transformation, cracking down on crime and rezoning key arteries such as 125th Street to make them more developer-friendly. Meanwhile, nonprofit groups, like the Harlem Children’s Zone, continued to invest in the community.

The effects have been striking. Luxury condo buildings, bougie shops, and a surge of new residents have appeared. According to census figures, whites went from 2 percent of Harlem’s population to 9.8 percent between 2000 and 2010. People of all ethnicities and income levels now consider Harlem when hunting for a Manhattan home, due largely to its real estate bargains. The average sale price of a two-bedroom unit here is $694,000; in SoHo, it’s $2.1 million. “Harlem has become a viable alternative to markets in the south,” says Jonathan Miller, president of real estate appraiser Miller Samuel.

But with change inevitably comes conflict. And perhaps no urban metamorphosis is more incendiary than the one taking place in Harlem, where Duke Ellington took the “A” train, Langston Hughes wrote racially charged poems, and Marcus Garvey launched his “Back to Africa” campaign. Tied to these memories is Harlem’s milieu: housing projects, stately brownstones, soul-food restaurants, jazz lounges, hair-braiding shops, and churches large and small. With gentrification in full swing, Harlem residents don’t just fear losing their homes; they fear losing their history, their culture.

Architecture plays a role in this saga. “It’s starting to look like downtown,” says Jaylene Clark, a young Harlem native who critiques the neighborhood’s gentrification in her new play, Renaissance in the Belly of a Killer Whale. A mile-long stretch of Frederick Douglass Boulevard reveals how quickly redevelopment can take hold. In recent years, more than a dozen condo developments, plus a chichi hotel and bevy of fashionable stores and eateries, have cropped up in the area, rebranded as SoHa (South Harlem). Architecturally, some recent structures refer to the existing buildings — mostly brick tenements rising five to eight stories. Others, however, contrast with their 19th-century counterparts in terms of scale and aesthetics. The Parc Standard, a modern, charcoal gray mid-rise designed by Architects Studio with Gene Kaufman, juts high above the roofline of two flanking buildings. The 28-unit Parc, with condos listed from $375,000 to $790,000, sold out within 11 months.

Surprisingly, Michael Henry Adams, a staunch local preservationist and author of Harlem: Lost and Found, is pleased with the new additions on Frederick Douglass Boulevard. For the most part, they “are quiet buildings that recede into the background and become good neighbors,” he says. “As a whole, it’s remarkably harmonious, particularly given what could have been there.” Once pockmarked with vacant lots, the area was rezoned in 2003 to promote residential and commercial growth. The new land-use regulations specified contextual design and capped building heights, preventing an invasion of glistening glass towers.

“You have to balance this need to develop properties and manage growth with a sensitivity toward what Harlem used to be, and what Harlem is to longtime residents. It’s not easy,” says Paimaan Lodhi, the district manager for Community Board 10, which covers central Harlem. The revitalization of Frederick Douglass Boulevard is a major success, he says, noting that crime has dropped 16.5 percent in 10 years and many of the new residential buildings contain affordable units. To critics of the redevelopment, he asks: “What’s the alternative? Vacant lots? Prostitutes and crack peddlers? We have a vibrancy there that we haven’t seen in decades.”

Even Clark acknowledges gentrification’s benefits. “I do feel safer,” the playwright says. But as for her preference for the old or new Harlem, there’s no simple answer. “In an ideal world,” she says, “I’d take elements of both and put them together.”

This story appeared in the September 2011 issue of Architectural Record.