ST. LOUIS  Several recent transactions are raising the possibility that this city’s downtown, a depressed office market with an overall vacancy rate of over 22 percent, may become a regional hub for computer software and data-center companies.

The deals include a decision by Unisys to locate a new software center in a century-old building a block from the riverfront and the expansion of several large data-center operations by other companies. The Unisys project in particular is seen by city officials and developers as a coup because St. Louis edged out the Minneapolis-St. Paul area and Salt Lake City to win the project.

Ted Davies, the president of Unisys’s federal systems business, said two factors were important in the choice of St. Louis. The first is proximity to the Rural Development agency at the Agriculture Department, which has a sizable office in the city and is expected by Unisys to be one of the new center’s main customers.

The second concern was the cost comparison between St. Louis and Reston, Va., where Unisys’s federal systems division has its headquarters. “We looked at labor and real estate and found the arbitrage to be about 25 percent,” Mr. Davies said.