The center span of a five-mile bridge being constructed across the Straits of Mackinac, connecting Michigan's two great peninsulas at mackinaw City on the lower, and St. Ignace on the upper. Designed by Dr. D. B. Steinman, this bridge has been engineered to withstand many times the recorded stresses of ice pressure, wind velocity, gravity and so forth. Overall length of bridge is 5 miles, has four lanes for traffic. Center span 3800 feet long between two 565-foot towers, water clearance of 150 feet. construction started in May 1954, scheduled for opening late in 1957.