The first underwater tunnel built in the U.S. — New York City’s Holland Tunnel, running beneath the Hudson River between New York and New Jersey — opened for traffic 85 years ago today. Despite its age, the tunnel remains a key traffic artery serving the New York City area, carrying more than 33 million cars and trucks every year. It is named for Clifford Holland, the project’s first chief engineer, who died of a heart attack at the age of 41, the day before the two halves of the tunnel were due to be joined. Heavy construction, such as bridges and tunnels, is a $17.8 billion a year industry in the U.S. You can find current data on the country’s economy — on the go — by downloading the new “America’s Economy” mobile application at <www.census.gov/mobile>.