It's been 15 years in the making – from acquiring land to finding tenants, but opening day is now less than a week away for East Harlem's big-box retail mall East River Plaza, located along the FDR Drive at 116th Street.

Costco will be the first to welcome shoppers, followed by other superstores like Target, Best Buy and Marshals in the coming year.

“I think it's going to be the catalyst of 116th Street becoming the next 125th Street,” says developer David Blumenfeld. “I think it’s time now that 116th sort of grows up and matures.”

East River Plaza is a joint venture of Blumenfeld Development Group and Forest City Ratner Companies. Developer David Blumenfeld first saw the site in the early 1990s, when most of the land was home to the abandoned Washburn Wire factory.

“Back in the early ‘90s, big box was first starting to explode on Long Island and in New York, Connecticut and New Jersey, and the numbers were phenomenal in the New York area, compared to other parts of the country,” Blumenfeld explains. “And I kept driving by this site on the FDR Drive, and I kept saying, ‘wow, this would be a great spot for big-box retailers.’”

But, he says, prospective tenants were not so easily convinced.

“I got a lot of strange looks at first, a lot of, ‘I don't think you know what you're talking about,’” recalls Blumenfeld. “We walked them around the site, we got up to some of their upper management and convinced them to do market studies and feasibility studies, and in the case of Costco, we looked at small businesses, we looked at people commuting together and breaking up bulk items.”

The other big problem for developers was small space. While a retail center of this nature in the suburbs would typically sit on 40 to 50 acres, the East River Plaza only covers six acres.

“We said maybe we can get two on top of one another, and then, well if we are building two, maybe we can build three and we wound up with five levels,” says the developer.

Customers pay to park at the elevated parking lot, with bridges connecting upper levels to garages. The total price tag of the development: a little over $500 million.

“A lot more than we expected,” Blumenfeld admits.

Once construction is completed and all the tenants have moved in, Blumenfeld says East River Plaza is expected to provide 1,200 -1,500 full-time jobs.

For now, its only store is Costco, which opens November 12th.