Cox, working with a team from billionaire Karp's New England Development and local property owners, laid the foundation for the multimillion dollar redevelopment of the area known as Waterfront West - between the Black Cow Restaurant and Route 1 - that could include residences, businesses and a hotel.
But Cox, a Plum Island resident, will no longer play a lead role in those changes. After two and a half years, he has decided leave Karp's firm to run his own real estate investment firm. Karp, who owns over two dozen buildings and lots in the downtown area, is one of Newburyport's biggest landowners.
"I really care about this community a ton," said Cox, a long-time real estate executive. "Another one of my dreams was to have my own development investment firm. It was an agonizing decision, but I had to try it now."
Cox's decision to leave raises questions about the status of the waterfront project. For over two years Newburyporters have waited to see what Karp wants to do, but so far no plans have been issued and Karp has remained mum.
Cox said the development team, operating under the name Newburyport Waterside Group, does not want to rush into a project.
"The next challenge is coming up with something we all like, people like and has economic vitality to it," Cox said. "That's the same in every development project."
Charles Lagasse, one of Karp's local partners, said there is no specific timeline when a plan will be released. But no plan will be revealed until the city has a new planning director.
"It's best if we wait so the planning director and the city can support a plan along with us," Lagasse said. "It's much better if we have a planning director (to work with), it makes things easier. We're watching for that."
A planning director is not expected to be hired until at least November.
Cox left New England Development to create Cox Development Group. Currently, he is working with other partners on two large industrial seaport distribution and warehouse projects in Boston and Seattle.
During his time working for New England Development, Cox worked closely with local property owners Charles and Ann Lagasse to form a unique business partnership. Karp's company purchased more than a dozen of Lagasse-owned properties in 2005.