The system, installed by the York Ice Machinery Corp. (later York International, which was acquired by Johnson Controls in 2005), was driven by six 1,000-hp compressor motors in the U.S. Capitol Power Plant that chilled more than 11 million gallons of water a day, according to a Johnson Controls blog post. The water was sent to the Capitol and the three other buildings, where coils and air-handling units cooled and dehumidified the various chambers and offices with about 2 million cubic feet of cool air each minute. Return water with the captured heat traveled back to the plant to be cooled in the closed-loop system. 

The $3.5 million — that’s roughly $79 million in today’s money — project began in 1933 and was completed on October 1, 1937. Johnson Controls says it was the world’s largest installation of refrigeration equipment for air-conditioning at the time. 

A grainy photo from the period shows an official Capitol Power Plant inspection group, including York President W.S. Shipley, House Speaker William Bankhead, and Architect of the Capitol David Lynn, looking serious, most of its members with hat in hand. 

A Library of Congress webpage with a 1938 photograph of the machinery inside the power plant includes the phrase, “No more hot air in Congress,” words that were, reportedly, often repeated in 1930s publicity about the system. 

“York is rightly proud of the magnitude, the precision, and efficiency of this intricate job of refrigeration,” said a full-page company ad in a 1937 issue of Time magazine. “This outstanding use of York equipment presents but a small part of refrigeration’s potent force in modern civilization.”