Founded in 1862, the original Union Pacific Rail Road was part of the first transcontinental railroad project, later known as the Overland Route.

In 1995, the Union Pacific merged with Chicago and North Western Transportation Company, completing its reach into the Upper Midwest.

However, due to intense lobbying by Dr. Thomas Clark Durant, the eastern terminal was moved to a location where the Union Pacific could link up with the Mississippi and Missouri Railroad in Iowa.

[4][5] Following the Act's passage, commissioners appointed by Congress began selling stock in the federally chartered Union Pacific Railroad Company.

By 1863, Durant had organized the purchase of 2,000 shares, the prerequisite amount of stock sold in order to begin the railroad's construction.

[6] The resulting track ran westward from Council Bluffs, Iowa, to meet in Utah the Central Pacific Railroad line, which had been constructed eastward from Sacramento, California.

[8] The two lines were joined at Promontory Summit, Utah, 53 miles (85 km) west of Ogden on May 10, 1869, hence creating the first transcontinental railroad in North America.

[19] To attract customers during the Great Depression, Union Pacific's chairman W. Averell Harriman simultaneously sought to "spruce up" the quality of its rolling stock and to make its unique locations more desirable travel destinations.

The same year that Union Pacific merged with the Chicago and North Western (1995), Burlington Northern and ATSF announced merger plans.

[30] The railway's Big Boy #4014, the world's largest operating steam locomotive, will visit 14 states in middle America in 2024.

Its "Heartland of America" tour begins in August 2024 in Cheyenne, Wyoming, and visits Arkansas, Colorado, Illinois, Iowa, Kansas, Missouri, Nebraska, Oklahoma and Texas through October.

[38] Union Pacific also closed facilities in Kansas City ("Neff yard"), Hinkle, Oregon, and Pine Bluff, Arkansas in 2019.

There is also a thin band of Signal Red along the bottom of the locomotive body, but this color has gradually become yellow as new Federal Railroad Administration (FRA) regulations for reflectorized tape came into effect in 2005; the trucks (painted Aluminum from 1955 to 1982), underframe, fuel tanks and everything else beneath that line are also Harbor Mist Gray.

Beginning in early 2002, a number of units were repainted with a large, billowing American flag with the corporate motto "Building America" on the side, where the 'UNION PACIFIC' lettering is normally positioned.

[44] From the second half of 2005 to the summer of 2006, UP unveiled a new set of six EMD SD70ACe locomotives in "Heritage Colors", painted in schemes reminiscent of railroads acquired by the Union Pacific Corporation since the 1980s.

[51] In April 2021, Union Pacific repainted an SD70M into a commemorative paint scheme called "We Are ONE" to honor Juneteenth and Pride Month.

[citation needed] The Chief Executive Officer of Union Pacific since August 14, 2023, is Jim Vena, the President is Beth Whited, and the chairman of the board is Mike McCarthy.

Disputes over trackage rights and passenger revenues with the C&NW prompted the UP to switch to the Milwaukee Road for the handling of its streamliner trains between Chicago and Omaha beginning in late 1955.

[96][97][needs update] The City of San Jose, California, threatened Union Pacific with a lawsuit in 2019 after years of complaints about transient and graffiti blight going unaddressed.

San Jose's mayor Sam Liccardo said"At any given conference of mayors, you won't hear anyone expressing confidence that Union Pacific will respond nimbly or collaboratively," and "But we are hopeful that the (memorandum of understanding) will turn a page on Union Pacific's behavior in the past to enable a more collaborative relationship going forward.

"[99]The Mercury News reports that company has been uncooperative and non responsive to working together, such as failing to come through with graffiti abatement as Union Pacific had promised the city.

In Logan, Utah, Union Pacific altered a construction agreement to require the city to pay maintenance fees in perpetuity for an upgraded crossing, a mandate which was against state code.

[100] The proposed legislation would make it easier for municipalities to get crossing improvements approved, and clarifies which party must pay associated maintenance costs.

[105] In January 2018, a former waste water operator at Union Pacific Albina Yard in Portland, Oregon, employed by the railroad's contractor Mott MacDonald negligently released thousands of gallons of oil into the environment.

An engineering firm hired by Union Pacific estimates 1,800 U.S. gallons (6,800 liters) of it was released into nearby Willamette River, not including the spill that was captured by the containment booms.

Employees of United States Environmental Protection Agency who were working at facilities nearby placed booms to contain the oil spill.

Federal prosecutors have charged the operator Robert LaRue Webb II with violation of the Clean Water Act for releasing the oil into the environment.

[107][108][109] In 2016, the Union Pacific Railroad Co. was named as a defendant in a lawsuit seeking cleanup of a contaminated rail yard site that operated in Lafayette, Louisiana, from the late 1800s until the 1960s.

[119] The company pays upkeep on the privately owned building, which houses part of Union Pacific's corporate collection, one of the oldest in the United States.

Holdings include weapons from the late 19th and 20th centuries, outlaw paraphernalia, a sampling of the immigrants' possessions, and a photograph collection comprising more than 500,000 images.