A great circle path is the shortest path between two points on a sphere. When applied to paths between two points on Earth, which is an oblate spheroid rather than a sphere, such paths are properly called geodesic paths. Winds aloft may make more circuitous paths faster but often the fastest path for an airplane is close to the geodesic path.
Until 150 years ago, going from New York to San Francisco involved a long ocean journey via Tierra del Fuego at the southern tip of South America or an arduous overland journey using horses and wagons. On 10 May 1869, the first transcontinental railroad across the United States was completed with a ceremonial golden spike at Promontory Summit, Utah, the culmination of a contruction effort by the Central Pacific Railroad east from Sacramento, California, and the Union Pacific Railroad west from Omaha, Nebraska. The railroads subsequently moved their interchange point southeast, to Ogden, Utah.
The path to the north of the Great Salt Lake had many curves and significant grades so between 1902 and 1904 the Southern Pacific Railroad, successor to the Central Pacific, built a 102-mile cutoff between Lucin and Ogden, including a causeway and an 11.88-mile trestle across the Great Salt Lake, shaving 44 miles off the route in addition to reducing curves and grades. In 1942, the original line was removed between Lucin and Corinne, Utah, with rail, spikes, and other metal being recycled for the war effort.
The trestle was costly to maintain so a dirt and rock causeway was contructed parallel to the trestle to the north. This causeway opened in 1959 though the trestle continued to see limited use until being dismantled in the mid-1970s. Since the original line across the Great Salt Lake was perfectly straight the parallel causeway resulted in a kink at each end; rail line is easily spotted from cruise altitude over northern Utah.
This weekend, a sesquicentennial celebration of the completion of this first U.S. transcontinental railroad will be held at the Golden Spike National Historical Park.
Today's Featured Map shows these railroad lines in northern Utah, including the original Central Pacific and Union Pacific portions, the Golden Spike location, and Southern Pacific's Lucin Cutoff with the 1959 causeway.
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Karl L. Swartz.
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