Question

in the gold rush of 1849, some one hundred thousand immigrants were lured to california by the promise of gold. towns and businesses popped up to accommodate the growing population, but a problem remained: how to communicate across the vast reaches of the united states. three businessmen thought they had an answer: faster mail delivery via the pony express, a relay system of horses and riders. the pony express made its first delivery on april 14, 1860. mail from st. joseph, missouri, reached san francisco in just eleven days, rather than a month or more, which was standard for mail delivery at the time. the pony express was a short - lived solution, however. after just eighteen months, it was replaced by a national telegraph wire.
what is the main, or central, idea of the passage?
the pony express allowed for faster communication in the rapidly growing united states.
the pony express was a chain of horses and riders across the country used to deliver mail.
on april 14, 1860, the pony express delivered mail from missouri to california in just eleven days.

Explanation:

The passage sets up the communication problem in the growing US post-1849 Gold Rush, introduces the Pony Express as a faster mail delivery solution, notes its speed, and then states its short lifespan. The first option captures the overarching context (growing US) and the core function of the Pony Express (faster communication), while the other options are just specific details from the text, not the central idea.

Answer:

The Pony Express allowed for faster communication in the rapidly growing United States.