The first Transcontinental Railroad (known originally as the "Pacific Railroad" and also as the “Great Transcontinental Railroad” and the “Overland Route”) was a continuous railroad line constructed between 1863 and 1869. It connected the existing eastern U.S. rail network at Omaha, Nebraska/Council Bluffs, Iowa with the Pacific coast on San Francisco Bay.
While Asa Whitney published his ideas on the idea of a railroad to California in 1849, others also joined the chorus. Eventually Theodore Judah, chief engineer for the Sacramento Valley Railroad, undertook a survey to find a manageable route through the Sierra Nevada mountains and presented his plan to Congress in 1856. The next stop on the timeline is July 1, 1862 when Congress passed the Pacific Railroad Act of 1862 which created the Central Pacific Railroad and the Union Pacific Railroad. In total, the rail line was built by the Central Pacific Railroad Company of California (CPRR), Union Pacific, and Western Pacific Railroad Company over public lands provided by extensive US land grants.
It opened for through traffic on May 10, 1869 when CPRR President Leland Stanford ceremonially drove the gold "Last Spike" (later dubbed the "Golden Spike") at Promontory Summit. The entire line wasn’t completed until November 1869 when the Central Pacific finally connected Sacramento to the east side of San Francisco Bay and Union Pacific connected Omaha to Council Bluffs completed the Union Pacific Missouri River Bridge in 1872.
The material here is just a fraction of what is written on the topic and is only intended to get researchers started - we do have an entry in This Month in Business History that replicates many of the sources below, but does contain additional resources. The following materials link to fuller bibliographic information in the Library of Congress Online Catalog. Links to digital content are provided when available.
Acts of Congress Relating to the Union Pacific RailroadA Congressional History of Railways in the United States by 
The Chinese and the Iron Road by 
Empire Express : Building the First Transcontinental Railroad by The First Transcontinental Railroad: Central Pacific, Union Pacific by 
Ghosts of Gold Mountain by History of the Union Pacific; a Financial and Economic Survey by 
Nothing Like It in the World by A Project for a Railroad to the Pacific by A Railroad to the Sea by 
Railroaded by Report ... of the United States Pacific Railway Commission [and Testimony taken by the Commission] by Report of Lieut. Col. James H. Simpson ... on the Union Pacific railroad and branches, Central Pacific railroad of California, Northern Pacific railroad, wagon roads in the territories of Idaho, Montana, Dakota, and Nebraska, and the Washington aqueduct by Reports of Explorations and Surveys, to Ascertain the Most Practicable and Economical Route for a railroad from the Mississippi River to the Pacific Ocean by Select Committee on Establishment of Railroad and Telegraphic Communication between the Atlantic States and the Pacific Ocean by Senatorial Excursion Party over the Union Pacific RailwaySpeech of Mr. Gwin, of California, on the bill to establish a railway to the Pacific, delivered in the Senate of the United States, January 13, 1853 by Union Pacific; the Building of the First Transcontinental Railroad by Additional works on the transcontinental railroad in the Library of Congress may be identified by searching the Online Catalog under appropriate Library of Congress subject headings. Choose the topics you wish to search from the following list of subject headings to link directly to the Catalog and automatically execute a search for the subject selected. For assistance in locating other subject headings which relate to this subject, please consult a reference librarian.
