Amos, an older contemporary of Hosea and Isaiah, was active c. 750 BCE during the reign of Jeroboam II, making the Book of Amos the first biblical prophetic book written. Amos lived in the kingdom of Judah but preached in the northern kingdom of Israel. His major themes of social justice, God's omnipotence, and divine judgment became staples of prophecy.
Amos was a prophet during the reign of Jeroboam ben Joash (Jeroboam II), ruler of Israel from 793 BCE to 753 BCE, and the reign of Uzziah, King of Judah, at a time when both kingdoms (Israel in the North and Judah in the South) were peaking in prosperity.