How did the transcontinental railroad affect communication? It made coast-to-coast communication happen almost instantly. It reduced coast-to-coast communication from a week to a day. It reduced coast-to-coast communication from months to weeks. It made coast-to-coast communication more complicated and costly.

The correct answer is: It reduced coast-to-coast communication from months to weeks.

Indeed, before the Transcontinental Railroad was completed it might take a traveler or settler months to do the same trip by wagon cart and weeks by boat through South America. By train it would take a traveler about two weeks to go from New York to San Francisco and in 1876 a train called the Transcontinental Express made the trip from New York to San Francisco in 83 hours and 39 minutes. It was not a regular train but a publicity stunt but it did show that the feat was possible.