Nationwide, median income is up by $1,600 year over year, while the poverty rate and percentage of Americans not covered by health insurance remained flat.

St. Louis is attracting young professionals in tech because of its affordability, said Ness Sandoval, an associate professor of sociology at St. Louis University.

Sandoval tracks migration trends in and out of the city and St. Louis area. He said both have seen a net gain in white residents, and a loss of black residents since the 2014 shooting of Michael Brown Jr. in Ferguson.

"Where we show white residents coming to the city, it's people from the East and West coast wanting to make the city itself their home," Sandoval said. "I think it's because it's a younger population, so those cities are just not as affordable compared to St. Louis." He mentioned Boston, New York, Washington, San Francisco and Denver as examples of cities where the cost of living can be too high for young professionals.

But the boon in employment and income isn't spread equally throughout the city, Sandoval suspects. He said much of the money being invested in the city's developments is going into the area between the Central West End and the downtown area.