In 1955, the Additional House Office Building Act was passed to allow more office space and parking around Capitol Hill. In the summer of 1962, the House Office Building Commission approved construction of two underground garages south of the Rayburn and Longworth House Office Buildings. Prior to this, members of Congress and their staff were parking on the grass and empty lots. Multilevel garages were approved to allow for more parking of an estimated more than 1,200 cars. Estimates in 1963 put the garage's overall cost at $8 million, or $5,800 per parking space.
Roll Call has several pictures from the years construction took place on the parking garages. The above photo is likely from 1968 — the garages were completed in March of that year. Below, we've included a bonus photo from construction. This was likely taken around 1965. Unfortunately, neither photo was captioned with a photo credit.