Question: Which railroad was acquired by the Union Pacific Corporation and became part of one of the world's largest transportation companies?

Context paragraphs:
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".

Kansas Pacific Railway: The Kansas Pacific Railway (KP) was a historic railroad company that operated in the western United States in the late 19th century.  It was a federally chartered railroad, backed with government land grants.  At a time when the first transcontinental railroad was being constructed by the Central Pacific and the Union Pacific, it tried and failed to join the transcontinental ranks.  It was originally the "Union Pacific, Eastern Division", although it was completely independent.  The Pennsylvania railroad, working with Missouri financiers, designed it as a feeder line to the transcontinental system.  The owners lobbied heavily in Washington for money to build a railroad from Kansas City to Colorado, and then to California.  It failed to get funding to go west of Colorado.  It operated many of the first long-distance lines in the state of Kansas in the 1870s, extending the national railway network westward across that state and into Colorado.  Its main line furnished a principal transportation route that opened up settlement of the central Great Plains, and its link from Kansas City to Denver provided the last link in the coast-to-coast railway network in 1870.  The railroad was consolidated with the Union Pacific in 1880, and its mainline continues to be an integral part of the Union Pacific network today.

History of the Union Pacific Railroad: The history of the Union Pacific Railroad stretches from 1862 to the present.  For operations of the current railroad, see Union Pacific Railroad; for the holding company that owns the current railroad, see Union Pacific Corporation.

Central Branch Union Pacific Railroad: The Central Branch Union Pacific Railroad was a railroad in the U.S. state of Kansas.  Originally planned as a line from Atchison west into Colorado, and given federal land grants by the Pacific Railway Act of 1862 as one of the branches of the Union Pacific Railroad, it was left with a hanging end at Waterville, Kansas when the Union Pacific Railway, Eastern Division, with which it was to connect, changed its route.  The line was acquired by the Union Pacific through a stock purchase by Jay Gould and leased to the Missouri Pacific Railroad in 1880.  In 1909 the Central Branch was merged into the Missouri Pacific; the latter company came back into the Union Pacific system in 1982.  In 1991 the remaining trackage west of Frankfort was leased to the Kyle Railroad.

Union Pacific (disambiguation): The Union Pacific is the largest rail system in the United States.  The rail system is owned by the Union Pacific Railroad, a Class I railroad owned by the Union Pacific Corporation.

Union Pacific Center: The Union Pacific Center at 1400 Douglas Street is one of downtown Omaha, Nebraska's newest high-rise buildings.  It houses the headquarters of the Union Pacific Railroad and its parent company, the Union Pacific Corporation.  It officially opened in June 2004 and rises 317 ft (97 m) making it the third tallest building in Omaha.  The old headquarters located directly across the street, was torn down in 2008 to make way for the new WallStreet Tower Omaha.

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.

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 ().

History of railroads in Colorado: The history of rail transportation in Colorado began with the competition between two separate railways in the late 1860s the Denver Pacific Railroad and the Colorado Central and Pacific Railroad.  Following the decision of the Union Pacific Railroad to route the transcontinental railroad through Cheyenne, Wyoming instead of Denver, the first town in the Front Range area to construct a connecting line to the Union Pacific Railroad would more naturally become the economic focus of the Colorado territory.  The Colorado Central and Pacific Railway was incorporated in 1865 by residents of Golden, however this railway was unable to immediately begin constructing a connecting line to Cheyenne.  The existence of the Colorado Central and Pacific Railroad prompted the citizens of Denver to incorporate the Denver Pacific Railroad on November 19, 1867.  Following a spirited campaign raising capital, the Denver Pacific Railroad laid its first track in 1869.  By June 26, 1870, the Denver Pacific Railroad was completed.

UPS Freight: UPS Freight is the Less-Than-Truckload (LTL) trucking division of UPS.  UPS acquired on August 8, 2005, Overnite Transportation Company (and its subsidiary Motor Cargo) from the Union Pacific Corporation (parent company of the Union Pacific Railroad) for $1.25 billion.  On April 28, 2006, Overnite Transportation officially became UPS Ground Freight, Inc.  The logos on the doors of the Overnite tractors were covered with signs showing the operator as UPS Freight.  UPS Freight soon changed the color scheme of the tractors from blue and grey to UPS brown on the bottom, with a gold line near the center of the tractor and gray for the upper color.  All new vehicles purchased by UPS Freight LTL come painted in these colors as the older Overnite equipment is replaced, while the new tractors for the truckload division (Former Overnite Transportation – Special Services Division) are solid white with the UPS shield on the roof fairing.

Supporting paragraphs: Western Pacific Railroad Union Pacific Railroad
Answer: Western Pacific Railroad