Tyndale Open Study Notes2 Chronicles 27

Jotham became king after sharing the throne with his father, Uzziah, for eleven years, from 750 to 740 BC. He then ruled alone for five more years, from 740 to 735 BC, totaling sixteen years. Jotham lived at least four more years, as Hoshea rose to power in the northern kingdom in the twentieth year of Jotham son of Uzziah (2 Kings 15:30). However, Jotham's son, Ahaz, had already started ruling alongside him. After Jotham's sixteen official years, Ahaz took over as king (see study note on 2 Kings 16:1–2). Ahaz likely had his official accession ceremony after Jotham's death in 732 BC, so the author of 2 Chronicles counts Ahaz's official reign starting in 731 BC (see 2 Chronicles 28:1).

Jotham continued the restoration work started by his father, Uzziah. He built fortresses and towers in the forests. These served as lookouts and highway defenses within the kingdom and on the frontier.

Uzziah received tribute from the Ammonites (2 Chronicles 26:8), and Jotham continued to control their land east of the Jordan. These payments stopped after three years, possibly because Jotham was busy fighting Israel and Aram (2 Kings 15:37).