One of Baltimore’s most ambitious — and delayed — waterfront projects is parting ways with its lead developer.

In a social media posting late Thursday, New York-based MAG Partners said it will be leaving the Baltimore Peninsula project in the coming months.

A source with knowledge of the situation said the ownership of Baltimore Peninsula decided against renewing its contract with MAG.

Baltimore Peninsula is primarily owned by Under Armour CEO Kevin Plank’s development firm and the investment bank Goldman Sachs.

The mega-development project in the neighborhood formerly known as Port Covington has gone through several iterations since Plank announced his plans to transform the former industrial area into a sparkling mini-city akin to Dubai roughly a decade ago.

In 2022, MAG Partners replaced the original development company hired by Plank’s ownership team. In its nearly four years, MAG oversaw the completion of phase one and the rebrand to Baltimore Peninsula.

While leasing at the mixed-use development has picked up in recent months, with MAG announcing several new tenants in the mixed-use development, it has fallen short of initial expectations.

Much of the office and retail space remains unoccupied, according to the most recently available public disclosures.

MAG said in the posting about its departure that Baltimore Peninsula has opened 1.1 million square feet of mixed-use development that includes more than 450 residential units.

Just a fraction of Plank’s original vision has been built.

The project has benefited from a variety of state and federal tax incentives, as well as an unprecedented $658.6 million in bonds approved by the city a decade ago.

Most of those bonds, which will be repaid over decades by property taxes, have yet to be issued.

Under Armour opened its new headquarters at Baltimore Peninsula last year, though the campus is far smaller than what Plank had originally envisioned.

After the Baltimore-based apparel company began struggling in 2016, the developers tried to lure Amazon’s HQ2. When that didn’t work, the site was rebranded as Cyber Town USA, then as Baltimore Peninsula.

When it joined the development team in May 2022, MAG — whose projects have included The New York Times building, Barclays Center and Pacific Park in Brooklyn, New York — was seen as giving Plank’s project development and investment heft.

It’s unclear what the next phase of development will be.

“I want to thank the Baltimore community and their elected representatives for their trust and partnership throughout this journey, your belief made it possible to turn vision into reality,” CEO MaryAnne Gilmartin said in a statement. “And finally, my gratitude to Kevin Plank, whose big dreaming and steadfast faith in Baltimore made all of this possible.”

Another co-developer, San Francisco-based MacFarlane Partners, will also be leaving the project.

Banner reporter Hallie Miller contributed to this story.