MOS was just a cowboy, or a shepherd. We could even call him a farmer. A few decades before the Assyrians came to wipe Israel off the map, God sent this man Amos up from Judah to preach to his distant relatives to the north. Incidentally, He would have been a contemporary of Hosea the prophet (compare Hosea 1:1 & Amos 1:1).
You should recall that Joel's prophecies came on the heels of a great "act of God" kind of natural disaster... a plague of locusts. The beginning of Amos' prophecies was also connected with a disaster, but it was an earthquake in this case, and this message preceded the disaster (vs. 1). It is particularly interesting that even though this man was an obscure farmhand, he preached a big message that had broad regional ramifications for the nations immediately surrounding Israel.
He began with Damascus of Syria (vs. 3) and moved around in his oration to address the Philistines of Gaza and Ashkelon (vs. 6-8), the people of Tyre (vs. 9-10), the descendants of Esau (vs. 11), the Ammonites (vs. 13) and the Moabites (Amos 2:1). But he circled only briefly and the bulk of the rest of the book is addressed to the northern kingdom of Israel.