One block off Market Street, in an area that officials hope will begin to spread development west, is the site of a former parking garage that has been razed. Construction on the site will start in April for a 231-unit apartment building covering 215,000 square feet. The demolition was a challenge because part of the old structure was built as a bomb shelter, reflecting its origin in 1956 at the height of the Cold War, Mr. Hare said.

In recognition of shifting demographic demands, all the new housing will be for rent only, and will be within walking distance of Amtrak and rail services at Wilmington Station.

In an earlier effort to reduce the amount of empty space in downtown buildings, Wilmington’s city government created a $15 million Upstairs Fund in 2008 to help landlords modernize upper floors that had been left vacant because the weak local market would not support the cost of renovating the space.

The public money — which is now exhausted — leveraged $45 million in private funds for 45 residential units that were built above street-level retail space, said Jeff Flynn, the city’s director of economic development.

City officials recognized a need to act in an area where the market alone was unable to spur renovation of the empty properties, Mr. Flynn said.

“To us, they are infrastructure,” he said. “We couldn’t sit back and let that happen.”

Other city measures for millennial-friendly businesses have included a $35,000 loan to La Fia, a restaurant on Market Street that was unable to obtain private financing for furniture and signage to enable it to open in 2007, and a $30,000 loan to the Ninth Street Bookshop, which opened two years ago a few blocks north.