The U.S.'s First Transcontinental Railroad was built between 1863 and 1869 to join the eastern and western halves of the United States. Begun just before the American Civil War, its construction was considered to be one of the greatest American technological feats of the 19th century. Known as the "Pacific Railroad" when it opened, this served as a vital link for trade, commerce, and travel and opened up vast regions of the North American heartland for settlement. Shipping and commerce could thrive away from navigable watercourses for the first time since the beginning of the nation. Much of this route, especially on the Sierra grade west of Reno, Nevada, is currently used by Amtrak's "California Zephyr", although many parts have been rerouted.