Final answer:
The Transcontinental Railroad, completed in 1869, marked the end of the wagon era by allowing much faster Westward travel and it catalyzed industrial expansion and urbanization in the United States.
Step-by-step explanation:
With the completion of the Transcontinental Railroad in 1869, the era of lengthy wagon travel for Westward expansion came to a close. This monumental accomplishment allowed what previously took many arduous months in horse- or oxen-drawn wagons to be accomplished in about a week. The railroad quickly became the nation's first "big business," significantly speeding up the development of other industries.
After the completion of the first Transcontinental Railroad at Promontory Point, Utah, on May 10, 1869, with the driving of the "Golden Spike," additional railroads were constructed. These included lines connecting various parts of the United States, further revolutionizing transportation and the economy.
The Homestead Act of 1862 also spurred Westward migration by providing land incentives for households to move west.
The industrial expansion post-Civil War, which included development in steel manufacturing, telecommunication, and electric light, was in part fueled by the extensive railroad network. The railroads transported vast mineral resources from the western states, aiding industrialization and urbanization, at the cost of native lands and living conditions that spurred the growth of labor unions.