The last mainframe supposedly enjoyed "quasi-celebrity status" within the House data center, having spent 12 years keeping the House's inventory control records and financial management data, among other tasks. But it was time for a change, with the House spending $30,000 a year to power the mainframe and another $700,000 each year for maintenance and support.

The cost and energy savings contribute to the program designed to improve efficiency in the halls of Congress. Applications running on the last mainframe have been moved to x86 and Unix servers, many of which are using technology that first appeared on the mainframe decades ago. 

"It's a symbolic transition into the latest and greatest in terms of green technology, virtualization, consolidation and all those things," says Jack Nichols, director of enterprise operations at the House of Representatives. "The mainframe plug was pulled, but it was pulled in favor of something that was started in the mainframe world." 

The House had been using mainframes since at least the early 1970s, and at one time had a 13,000-square-foot data center dedicated to mainframe and mainframe operations. As mainframes grew stronger, the House moved down to just one machine, in addition to other types of servers. The last mainframe was an IBM model in place since 1997, and was situated in the Office Building.