The Utah Northern Railway was the first to enter Idaho Territory. It was a narrow gauge line connected to the Union Pacific mainline at Ogden.

Starting in 1871, Mormon farmers in Cache Valley, Utah, volunteered their labor and their teams to grade the first 75 miles of road bed in the hope that the railroad would give them and their produce better access to the markets of Ogden and Salt Lake City.

By May 1874, construction had stopped at Franklin, just across the state line in Idaho. The great financial panic of 1873 had made investors cautious, and the company went bankrupt in 1878. At the foreclosure sale, financier Jay Gould, a man often labeled a "robber baron," came up with the money that allowed the Union Pacific to buy the Utah Northern and to form a new company named the Utah & Northern.

The objective was now more ambitious - to reach the copper mines of Montana centered at Butte. The electrical age just beginning was creating a large and growing demand for copper of all kinds, but especially for copper wire. Within the decade, some Idahoans were enjoying the benefits of the telegraph, the telephone, and electric lights.

The first steel bridges in Idaho were installed on the Utah & Northern Railway's line to the copper mines of Montana. Two of them arrived in Ogden by Union Pacific trains in April 1879. They had been pre-fabricated by the King Bridge Co. of Cleveland. The Idaho World reported that a crew of 75 men would erect the bridges across the Snake River at Eagle Rock (which and Blackfoot.

The one at Eagle Rock, pictured above, was put up right next to Matt Taylor's 1865 wooden toll bridge. When 200 feet of the bridge at Blackfoot fell into the river in June 1881, the Statesman said that the King Bridge Co. had guaranteed it for 18 months and promised to re-erect it.

Later that year, as the Oregon Short Line began building westward across the Snake River plain, three wooden truss bridges, each 180 feet long, and a 250-foot steel bridge were being built to span the Snake River at American Falls.

The Idaho Statesman received a visit from E. Lane, superintendent of the Union Pacific bridge department, who described the progress being made: "The grade of the road has been nearly completed, the bridges are being put in and work is progressing on the bridge across the river. This bridge is to be composed of four spans, resting on two abutments and three piers. These piers are of solid masonry, resting on a rock foundation, and stand 26 feet above the water. The falls are divided by a rocky island about 100 feet in width. On one side of the island the descent of water is a perpendicular fall of 29 feet, while on the other side the fall is more like rapids, descending the same distance in a run of about 300 feet. The bridge passes about over the center of this sloping fall, while the vertical fall will be nearly under the bridge, thus giving the passenger a fine view as he passes over." The one steel span was being built in Chicago by Rust & Coolidge.

In October 1894, the Oregon Short Line began replacing its wooden bridges with steel ones. All of the new structures would use the Pegram truss, a unique bridge type that had been patented by young engineer George H. Pegram in 1885. After earning a degree in civil engineering from Washington University in St. Louis, his first job was on the engineering crew for the Utah & Northern in 1878 and '79 when the survey for a new route north to Montana was being made.

Pegram would work for several other railroad companies before making his important contribution to Idaho railroad history with the Pegram truss.

The Idaho Statesman listed the six wooden bridges being replaced: one at American Falls, one at Caldwell across the Boise River, two across the Snake River near Nyssa, Ore., and two across the Snake near Ontario. Thanks to the efforts of Donald W. Watts at the Idaho State Historical Society, these bridges and their history have been researched in detail. His findings were published in the prestigious Journal of the West in 1992.

Two sections from the bridge at Ontario were installed over the Big Wood River near Ketchum in 1917, replacing wooden bridges built for the Wood River branch of the Oregon Short Line in 1882. The railroad tracks are gone, but these bridges now have wooden decking and guard rails and are part of a popular bicycling and hiking trail that runs through the valley. Watts located other Pegram trusses that once crossed the Snake near Weiser or Ontario at St. Anthony, where they were relocated to cross the upper Snake in 1914. Only a few of the Pegram truss bridges survive.

When George Pegram retired as chief engineer for the Union Pacific Railroad in 1898, the company honored his years of service by naming a town on the mainline after him. Pegram, Idaho, is a tiny place in the southeastern part of the state, not far from where his career began as an engineer.

Arthur Hart writes this column on Idaho history for the Idaho Statesman each Sunday. E-mail histnart@mindspring.com.