Review the details below. The transcontinental railroad allowed access to previously untapped natural resources from the West and Midwest, leading to a boom in U S. manufacturing. Freight and passengers crossed from the East to the West more quickly and cheaply than ever before once the transcontinental railroad was completed in 1869. Smaller railroads connected to the transcontinental opened new lands to settlement and allowed thousands of new towns to be built. Choose the best topic sentence to introduce a paragraph containing these details. Industries on the East Coast produced more goods once the transcontinental railroad was finished. The transcontinenta I railroad benefitted the American economy by opening up the Midwest and West Coast to the rest of the U.S. Americans traveled to thousands of new places in the West as a result of the transcontinental railroad.