How were Telegraph lines maintained in the 1800s?

I was just watching the Civil War episode of "America: A History of Us" and I was struck by this question.

If any of you have ever seen this show, it mentions the importance of the telegram in this war, particularly for the Union. It even mentions that Lincoln himself used it to issue orders on the battlefield.

I'm left baffled on how this technology was maintained so early in its life. Just today I saw the Comcast folk riding their cherry-pickers to fix downed telephone lines. How were these lines maintained through inclement weather? Were they ever considered as targets for the enemy? Or do I have a completely simplistic view of how these lines work?