PHILADELPHIA—As retailers continue to go vertical, look for a major city promoting its downtown—along with a baby boom. "We've been putting our resources together, including everything from event marketing to public relations, helping retailers from beginning to end," says Anne Nevins, vice president of market development for the Philadelphia Industrial Development Corp.

In the past decade, Center City's population has grown by 10%, with some 179,000 residents calling the trade area home, the city says. Greater Center City experienced a 53% increase in median household income between 2000 and 2010. According to the just-released Center City District annual retail report, demand for goods within one mile of City Hall reached $710.9 million this past year, up from $491.5 million in 2010. Adding to that market is a growing tourism base, with three new hotels already under construction and a fourth slated to begin building by year-end.

"We are looking for new and better retail to supplement what we have," says Michelle Shannon, VP of marketing and communications for Center City District/Central Philadelphia Development Corp. "There are people who have an outdated perception of the city."