<P> Former Union General John "Jack" Casement was hired as the new Chief Engineer of the Union Pacific . He equipped several railroad cars to serve as portable bunkhouses for the workers and gathered men and supplies to push the railroad rapidly west . Among the bunkhouses Casement added a galley car to prepare meals, and he even provided for a herd of cows to be moved with the railhead and bunk cars to provide fresh meat . Hunters were hired to provide buffalo meat from the large herds of American bison . </P> <P> The small survey parties who scouted ahead to locate the roadbed were sometimes attacked and killed by raiding Native Americans . In response, the U.S. Army instituted active cavalry patrols that grew larger as the Native Americans grew more aggressive . Temporary, "Hell on wheels" towns, made mostly of canvas tents, accompanied the railroad as construction headed west . </P> <P> The Platte River was too shallow and meandering to provide river transport, but the Platte river valley headed west and sloped up gradually at about 6 feet (1.8 m) per 1 mile (1.6 km), often allowing to lay a mile (1.6 km) of track a day or more in 1866 as the Union Pacific finally started moving rapidly west . Building bridges to cross creeks and rivers was the main source of delays . Near where the Platte River splits into the North Platte River and South Platte River, the railroad bridged the North Platte River over a 2,600 - foot - long (790 m) bridge (nicknamed 1⁄2 mile bridge). It was built across the shallow but wide North Platte resting on piles driven by steam pile drivers . Here they built the "railroad" town of North Platte, Nebraska in December 1866 after completing about 240 miles (390 km) of track that year . In late 1866, former Major General Grenville M. Dodge was appointed Chief Engineer on the Union Pacific, but hard working General "Jack" Casement continued to work as chief construction "boss" and his brother Daniel Casement continued as financial officer . </P> <P> The original emigrant route across Wyoming of the Oregon, Mormon and California Trails, after progressing up the Platte River valley, went up the North Platte River valley through Casper, Wyoming, along the Sweetwater River and over the Continental Divide at 7,412 feet (2,259 m) South Pass . The original westward travellers in their ox and mule pulled wagons tried to stick to river valleys to avoid as much road building as possible--gradients and sharp corners were usually of little or no concern to them . The ox and mule pulled wagons were the original off - road vehicles in their day, since nearly all of the Emigrant Trails went cross country over rough, un-improved trails . The route over South Pass's main advantage for wagons pulled by oxen or mules was a shorter elevation over an "easy" pass to cross and its "easy" connection to nearby river valleys on both sides of the continental divide for water and grass . The emigrant trails were closed in winter . The North Platte / South Pass route was far less beneficial for a railroad, as it was about 150 miles (240 km) longer and much more expensive to construct up the narrow, steep and rocky canyons of the North Platte . The route along the North Platte was also further from Denver, Colorado, and went across difficult terrain, while a railroad connection to that City was already being planned for and surveyed . </P>

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