How did the Union Pacific Railroad acquire supplies to build the transcontinental railroad?

The Union Pacific Railroad was one of the two companies that were tasked with building a transcontinental railroad. The other one being the Central Pacific Railroad Company. These two companies were assigned the project after Abraham Lincoln signed the Pacific Railroad Act into law.

The act gave each company 6,400 acres of land (later doubled to 12,800) and $48,000 in government bonds for every mile of track built. This is how the Union Pacific Railroad acquired supplies to build the transcontinental railroad. Moreover, the act established also established that the Central Pacific Railroad Company would start building in Sacramento and continue across the Sierra Nevada, while the Union Pacific Railroad would build westward from the Missouri River, near the Iowa-Nebraska border.

America's first steam locomotive made its debut in 1830, and over the next two decades railroad tracks linked many cities on the East Coast. By 1850, some 9,000 miles of track had been laid east of the Missouri River. During that same period, the first settlers began to move westward across the United States; this trend increased dramatically after the discovery of gold in California in 1849. The overland journey-across mountains, plains, rivers and deserts-was risky and difficult, and many westward migrants instead chose to travel by sea, taking the six-month route around Cape Horn at the tip of South America, or risking yellow fever and other diseases by crossing the Isthmus of Panama and traveling via ship to San Francisco.