The redevelopment of Chicago’s Old Main Post Office took a major step forward as global healthcare firm Walgreens announced a plan to move 1,800 employees to the long-vacant Art Deco structure at 433 W. Van Buren Street.

First reported Thursday evening by the Chicago Tribune and confirmed Monday at an onsite press conference held by Chicago Mayor Rahm Emanuel, the deal represents the first tenant commitment for space within the 2.8-million-square-foot office conversion project.

Walgreens’ 200,000-square-foot lease—roughly the equivalent of one floor within the massive structure—will house the company’s IT, digital, mobile, and e-commerce operations as well as the Walgreen’s University training program.

Although the firm is expected to still maintain a strong presence at its current corporate headquarters in Deerfield, Illinois, it will shift 1,300 positions from the suburbs and consolidate 500 existing downtown workers to the 4th floor of the Post Office.

The news comes four years after reports that Walgreens was looking to relocate its entire HQ to the vacant riverfront building. That deal never went through and eccentric British multimillionaire Bill Davies later sold the property to current owners 601W Companies. Unfortunately, the Brit passed away just days before the sale was finalized.

Billed as the largest adaptive reuse project in the nation, the Post Office redevelopment was designed by the Chicago office of global architecture firm Gensler. The $600 million renovation plan includes the restoration of the building’s historic lobby as well as the addition of a food hall, three-acre rooftop terrace, public riverwalk, and no less than 2,400 new windows.

With interior work ongoing since early 2017, the Post Office hopes to welcome Walgreens by the fall of 2019. The hulking 1920s-era building—along with the nearby redevelopment of Union Station—was included as one of ten sites listed in Chicago’s official bid for Amazon’s HQ2 campus.

The company is expected to announce a winner some time this year and, although Chicago made Amazon’s 20-city short list, the Walgreens move is a clear indication that the iconic building straddling Congress Parkway is coming back life with or without help from the Seattle-based e-commerce giant.

Mayor Emanuel touring the 4th floor of the Old Post Office, where Walgreens plans to convert it into an open work environment. The Department is glad to assist, as they convert the long vacant building. pic.twitter.com/1lybnuQkUR — Chicago DOB (@ChicagoDOB) June 18, 2018