At the time, most people lived pretty isolated from each other. There was no radio or television or even telephone yet. Most of the population communicated via letters and got their information from newspapers.
During the 1850s, correspondence was still very slow though, so if we're just taking speed of delivery into account, the telegraph would've been the most viable option. This resource wasn't available everywhere because it still relied on a direct wiring system and it was also very expensive. Atlanta and New York City are close enough so they could communicate with telegraph and it would've certainly been the fastest way at the time.
Hope this helps!