ST. LOUIS • Once the heavy-duty electrical connections are completed, XIOLINK's new headquarters will open as the latest example of information technology businesses that are expanding downtown.

Relatively cheap electricity and the infrastructure needed to deliver it are main reasons why IT firms are locating downtown, company executives say. Also key is the ability to connect to the vast network of fiber lines AT&T installed for its communication center on Pine Street.

XIOLINK plans to open its $13 million headquarters, at 1111 Olive Street, on Sept. 1.

Around the corner, at 210 North Tucker Boulevard, is Digital Realty Trust. The San Francisco-based IT company has amped the building's juice by 16 megawatts, effectively quadrupling the power available to the 18-story structure and is adding as much as 60,000 square feet of data center space at the 200,000-square-foot building.

Glenn Benoist, Digital Realty's vice president of portfolio management, said increased demand for IT services prompted the improvements.

"Data center facilities like 210 North Tucker are a critical asset for St. Louis' economy because they provide the infrastructure for companies' computing systems, which allow them to grow, create jobs and build the tax base," he said.

"St. Louis is a very important market for us because it is such a desirable location for data centers."

The city began promoting development of IT companies about five years ago with $250,000 to fund a "tech incubator" at 210 North Tucker. Barbara Geisman, the city's deputy mayor for development, said the goal was to lure companies that would want to use the existing fiber network.

"We've got this AT&T data center that has all these fiber options," she said. "We have great communication infrastructure downtown."

Digital Realty said it has nearly two dozen tenants at its North Tucker building and its fully leased data center at 900 Walnut Street, where 11-year-old XIOLINK has operated since 2003. AmerenUE's underground power grid serves 210 North Tucker, which also has its own generators. Connecting the Tucker and Walnut buildings are 400 strands of high-capacity fiber, company officials said.

Brad Pittenger, XIOLINK's chief executive, said the company outgrew its space on Walnut and wanted to expand downtown.

In February, the state awarded XIOLINK nearly $850,000 in brownfields tax credits to pay for removal of asbestos and other hazardous material from 1111 Olive. In March, the city approved $2.4 million in tax-increment financing.

The project also receives state and federal historic tax credits, as it is on the National Register of Historic Places.

Downtown's emergence as a data hub "is definitely really happening," Pittenger said.

Over time, XIOLINK will employ more than 50 at its location on Olive while keeping its current 25 or so workers on Walnut. The company bought the five-story 1111 Olive building in part because its floors are able to bear the weight of racks and racks of computers.

Built strong enough in 1917 for Post-Dispatch presses, the structure also housed KSD radio, beginning in 1922. After an Art Deco remodeling in the early 1940s, the building was the first home of KSD-TV, which began broadcasting in 1947.

After the station, now KSDK, moved to Market Street, a printing business and the United Way occupied the Olive location. It was vacant when XIOLINK took over this year.

Pittenger said downtown's ample supply of electricity and large fiber network make it a good fit for his company.

"All that fiber is out there under the street," he said. "We just have to bring it into our building."

Workers dismantled the unused 500-foot broadcast tower this spring. Pittenger noted that the building erected as a place for printing presses now houses the latest in electronic data storage and Web hosting. He said XIOLINK plans two more expansions over the next four years at a combined cost of as much as $19 million.

In terms of employment, the largest IT project under way downtown is a project by Unisys Corp. It plans to open this fall a center employing as many as 300 people by 2012.

"We like the city concept," Steve Moritz, the company's general manager of tech services, said when Unisys announced the project in June.

"We think it's an attractive location, particularly for the younger IT workers."

A Unisys spokesman said Thursday that the project remains on schedule although the company had yet to choose the site for its downtown center. The company will initially use about 10,000 square feet of space for 75 workers. Space requirements include the ability to grow to about 45,000 square feet to accommodate 300 employees.

To help lure Unisys, based in suburban Philadelphia, the state awarded the company $4.5 million in Missouri Quality Jobs Program tax credits, $900,000 in New Jobs Training funding and $212,500 in recruitment help.

The Regional Chamber and Growth Association said its study showed that 300 Unisys jobs, with an average annual salary of $55,000, would produce 355 additional indirect jobs and a $82.4 million direct and indirect impact on the region's economy.

Geisman said the city is happy to have the growing number of "knowledge workers," many of them downtown residents. She said IT demand at the Walnut building is so great that a former ground-floor restaurant "is now filled with techie guys."