Question: The Las Vegas and Tonopah Railroad was a 197.9 mile railroad.that ran northwest from a connection with the mainline of the San Pedro, Los Angeles and Salt Lake Railroad at Las Vegas, Nevada, the SPLA&SL railroad later became part of which freight hauling railroad that operates 8,500 locomotives over 32,100 route-miles in 23 states west of Chicago and New Orleans?

full_context: Document 1: Union Pacific Corporation: The Union Pacific Corporation (or simply Union Pacific) is a publicly traded stock holding company that was established in 1969 and it is the parent company of the current form of the Union Pacific Railroad. The company's stock symbol is ().
Document 2: Wells Fargo Rail: Wells Fargo Rail is the new name for the historic First Union Rail Corporation, along with the combined business of the former GE Capital Rail Services, which Wells Fargo purchased from GE in September 2015. The new company/name took effect January 1, 2016, and is based in Rosemont, Illinois, USA. Wells Fargo Rail is the largest railcar and locomotive leasing company in North America with over 175,000 railcars and 1,800 locomotives available.
Document 3: Norfolk Southern Railway: The Norfolk Southern Railway (reporting mark NS) is a Class I railroad in the United States. With headquarters in Norfolk, Virginia, the company operates 36,200 route miles in 22 eastern states, the District of Columbia, and has rights in Canada from Buffalo to Toronto and over the Albany to Montreal route. NS is responsible for maintaining 29,000 miles, with the remainder being operated under trackage rights from other parties responsible for maintenance. The common commodity hauled on the railroad is coal from mines in Indiana, Kentucky, Pennsylvania, Tennessee, Virginia, and West Virginia. The railroad also offers the largest intermodal network in eastern North America.
Document 4: Los Angeles and Salt Lake Railroad: The Los Angeles and Salt Lake Railroad (reporting mark SLR) was a rail company that completed and operated a railway line between its namesake cities, via Las Vegas, Nevada. Incorporated in Utah in 1901 as the San Pedro, Los Angeles and Salt Lake Railroad, the line was largely the brainchild of William Andrews Clark, a Montana mining baron and United States Senator. Clark enlisted the help of Utah's U.S. Senator Thomas Kearns, mining magnate and newspaper man, to ensure the success of the line through Utah. Construction of the railroad's main line was completed in 1905. Company shareholders adopted the LA&SL name in 1916. The railway was also known by its official nickname, "The Salt Lake Route", and was sometimes informally referred to as "The Clark Road". The tracks are still in use by the modern Union Pacific Railroad, as the Caliente, Sharp, and Lynndyl Subdivisions.
Document 5: Railroad Cottage Historic District: The Railroad Cottage Historic District, in Las Vegas, Nevada, was constructed by the San Pedro, Los Angeles & Salt Lake Railroad to provide housing for the railroad's workers.
Document 6: Western Pacific Railroad: The Western Pacific Railroad (reporting mark WP) was a Class I railroad in the United States. It was formed in 1903 as an attempt to break the near-monopoly the Southern Pacific Railroad had on rail service into northern California. WP's Feather River Route directly competed with SP's portion of the Overland Route for rail traffic between Salt Lake City/Ogden, Utah and Oakland, California for nearly 80 years. In 1983, the Western Pacific was acquired by the Union Pacific Corporation and it was soon merged into their Union Pacific Railroad. The Western Pacific was one of the original operators of the "California Zephyr".
Document 7: Northern Transcon: The Northern Transcon, a route operated by the BNSF Railway, traverses the most northerly route of any railroad in the western United States. This route was originally part of the Chicago, Burlington and Quincy Railroad, Northern Pacific Railway, Great Northern Railway and Spokane, Portland and Seattle Railway systems, merged into the Burlington Northern Railroad system in 1970.
Document 8: Nevada County Narrow Gauge Railroad: The Nevada County Narrow Gauge Railroad (NCNGRR) (nickname: "Never Come, Never Go") was located in Northern California's Nevada County and Placer County, where it connected with the Central Pacific Railroad. The Nevada County Narrow Gauge Railroad Company incorporated on April 4, 1874, and was headquartered in Grass Valley, California. After two years of construction, passenger and commercial rail services began in 1876 and continued until 1943. The 22.53 mi line ran from Colfax, north through Grass Valley to Nevada City. At one time, the railroad was notable for having the highest railroad bridge in California, the Bear River Bridge, built in 1908.
Document 9: Northern Pacific Railway: The Northern Pacific Railway (reporting mark NP) was a transcontinental railroad that operated across the northern tier of the western United States, from Minnesota to the Pacific Northwest. It was approved by Congress in 1864 and given nearly 40000000 acre of land grants, which it used to raise money in Europe for construction.
Document 10: Las Vegas and Tonopah Railroad: The Las Vegas and Tonopah Railroad was a 197.9 mile railroad built by William A. Clark that ran northwest from a connection with the mainline of the San Pedro, Los Angeles and Salt Lake Railroad at Las Vegas, Nevada to the gold mines at Goldfield. The SPLA&SL railroad later became part of the Union Pacific Railroad and serves as their mainline between Los Angeles and Salt Lake City.
Document 11: CSX Transportation: CSX Transportation (reporting mark CSXT) is a Class I railroad in the United States. The main subsidiary of the CSX Corporation, the railroad is headquartered in Jacksonville, Florida, and owns about 21,000 route miles (34,000 km). CSX operates one of the three Class I railroads serving most of the East Coast, the other two being the Norfolk Southern Railway (NS) and Canadian Pacific Railway. It also serves the Canadian provinces of Ontario and Quebec. Together CSX and Norfolk Southern Railway have a duopoly over all east-west freight rail traffic east of the Mississippi River. As of August 8, 2017, CSX's total public stock value was slightly over $41.5 billion.
Document 12: Los Angeles &amp; San Pedro Railroad: The Los Angeles & San Pedro Railroad was Southern California's first railroad. Its 21 mile line from San Pedro Bay to Los Angeles was built from 1868 to 1869 and began operations on October 26, 1869. The railroad was the brainchild of Phineas Banning and its primary purpose was to transport freight from the port to the city.
Document 13: Denver, South Park and Pacific Railroad: The Denver, South Park, and Pacific Railroad (later called the Denver, Leadville and Gunnison Railway) was a historic narrow gauge railroad that operated in Colorado in the western United States in the late 19th century. The railroad opened up the first rail routes to a large section of the central Colorado mining district in the decades of the mineral boom. The railroad took its name from the fact that its main line from Denver ascended the Platte Canyon and traversed South Park. Founded in 1872 by Colorado Governor John Evans, the company was purchased by the Union Pacific Railway in 1880, though it continued to be operated independently. The line went bankrupt in 1889 and was reorganized under the new moniker the Denver, Leadville and Gunnison Railway. When the Union Pacific went bankrupt in 1893, the DL&G lines went into receivership and were eventually sold to the Colorado and Southern Railway. In the first half of the 20th century, nearly all the company's original lines were dismantled or converted into . The last train to run the old DSP&P tracks was from Como, Colorado on April 11, 1937. A section of the standard gauge line between Leadville and Climax is still operated as a passenger excursion railroad called the Leadville, Colorado and Southern Railroad. At its peak the Denver, South Park and Pacific Railroad had 335 mi of narrow gauge line, making it the largest narrow gauge railroad in the state of Colorado.
Document 14: Union Pacific Railroad: The Union Pacific Railroad (or Union Pacific Railroad Company and simply Union Pacific) is a freight hauling railroad that operates 8,500 locomotives over 32,100 route-miles in 23 states west of Chicago and New Orleans. The Union Pacific Railroad system is the largest in the United States and it is one of the world's largest transportation companies. The Union Pacific Railroad is the principal operating company of the Union Pacific Corporation (); both are headquartered in Omaha, Nebraska.
Document 15: Salt Lake and Utah Railroad: The Salt Lake and Utah Railroad, also known as the Orem Line or Orem Interurban, was an electric railroad which operated between downtown Salt Lake City and Payson, Utah. Construction of the main line begun in 1913. The railroad was financed by A. J. Orem & Company, with Walter C. Orem as president. The railroad opened in 1914 with stops in both Utah County and Salt Lake County. The railroad also operated a branch line which ran to Magna, Utah. Both passenger and freight service was offered. The line's terminus in downtown Salt Lake City was shared with the Bamberger Railroad, and was located at the current site of Abravanel Hall. The railroad stopped service in 1946.
ground_truth: Union Pacific Railroad