The Golden Gate Bridgeis celebrating its seventy-fifth anniversary.The bridge opened to vehicle trafficon May twenty-eighth, nineteen thirty-seven.Since then, more than two billion vehicleshave crossed the world famous structurebetween San Francisco and Marin County, California.As many as one hundred twelve thousand carsmake the trip each day.The Golden Gate Bridgehad the longest suspension span in the world,at the time it was built.The suspended roadway stretchesone thousand two hundred eighty metersbetween the bridge's two tall towers.Today it still rates among the top tenlongest bridge spans in existence.Mary Currie works for the Golden Gate Bridge,Highway and Transportation District.She says the bridge is one of the most extraordinaryengineering projects of all time.MARY CURRIE: "The Golden Gate Bridgeis an engineering marvel certainly,and it gets award after award after award for what it meansin civil engineering and structural engineering.It's also a place where things happen first.For example, we were the first suspension bridgeto have to change the roadway deck."The Golden Gate Bridge is named after the Golden Gate Strait.That narrow passage of waterconnects the San Francisco Bay to the Pacific Ocean.Joseph Strauss was the chief engineerof the Golden Gate Bridge project.Work began in nineteen thirty-three.The project took four years to complete.The bridge is two thousand seven hundred eighty-eight meters long from one end to the other.It is twenty-seven meters wide.Two large cables pass over the top of the bridge's towers.These structures stand two hundred twenty seven metersabove water and one hundred fifty two meters above the road.Each cable holds more than twenty-seven thousandfive hundred strands of wire.Two hundred fifty pairs of vertical suspender ropesconnect the support cables to the suspension bridge.This is part of what enables the bridge to move up and down by nearly five meters.The Golden Gate Bridge weighed eight hundredeleven million five hundred thousand kilogramswhen it was completed in nineteen thirty-seven.The San Francisco Chronicle newspapercalled the finished project,"a thirty-five million dollar steel harp!"Architect Irving Morrow gets creditfor the bridge's bright orange color.The Navy wanted the bridge painted in yellow and black.The Air Force had suggested red and white.MARY CURRIE: "But we were fortunate that Irving Morrowknew that that color would blend with the environment,it would contrast with the ocean and the air above,and it would also allow the art deco styling to really stand out."And that's the VOA Special English Technology Report,written by June Simms.Transcripts, MP3s and podcasts of our reports areat 51voa.com.We're also on Facebook and Twitter at VOA Learning English.