bridge. Construction began on 5 November 1962. Forty-five months later, six months ahead of schedule, the bridge was inaugurated on 6 August 1966. Presiding at the ceremony was the President of Portugal, Admiral Américo Thomaz. Also present were the Prime-Minister, António de Oliveira Salazar, and the Patriarch of Lisbon, Cardinal Manuel Gonçalves Cerejeira. The bridge was named Salazar Bridge (Ponte Salazar), after Prime Minister Salazar. United States Steel International Inc., based in New York, was prime contractor for the bridge. Morrison-Knudsen of Portugal Ltd., an American firm based in Boise, Idaho, was U.S. Steel's principal associate. Morrison-Knudsen had previously worked on the San Francisco Bay Bridge. The bridge was designed by Steinman, Boynton, Gronquist and London of New York, and Tudor Engineering Company of San Francisco. The steel was imported from the US. Four workers died, out of a total of 3,000 who worked on the site. Construction took a total of 2,185,000 man-hours of work. The total cost of the bridge came to 2.2 billion Portuguese escudos, or US$32 million (US$225 million in 2011 adjusted for inflation). Soon after the Carnation Revolution in 1974, the bridge was renamed the 25 de Abril Bridge, the day the revolution had occurred. A symbol of those times was captured on film, with citizens removing the large brass letters spelling "Salazar" from one of the main pillars of the bridge and painting a provisional "25 de Abril" in its place. Expansion The upper platform, running above water, had four car lanes, two in each direction, with a dividing guardrail. On 23 July 1990, the guardrail was removed and a fifth, reversible lane was created. On 6 November 1998, the side walls were extended and reinforced to make space for the present six lanes. Cars crossing the bridge make a peculiar hum - listen (59s) - because the two inner lanes are made of metallic grating rather than asphalt to minimize aerodynamic forces by means of pressure equalization. Since 30 June 1999, the lower platform has carried a double track railway. To accommodate that, the bridge underwent extensive structural reinforcements, including a second set of main cables, placed above the original set, and the main towers were increased in height. The railway had been part of the initial design, but was eliminated for economy, so the initial structure was lightened. The original builder American Bridge Company was called again for the job, performing the