Jotham did, however, build the Upper Gate of the house of the Lord, and he built a tower at the north end of the city called the wall of Ophel. He built cities in the mountains of Judah and fortresses and towers in the forests.
Jotham went to battle with the king of the Ammonites and his armies and defeated them. In making peace, the people of Ammon gave Jotham 100 talents of silver, (roughly $100,000), 100,000 bushels of wheat, and 100,000 bushels of barley. The people of Ammon also paid this to him in the second and third years.
Isaiah, Hosea and Micah all prophesied during the life and times of Jotham. Jotham's name is mentioned in Isaiah 1:1, 7:1, Amos 1:1 and Micah 1:1. Some of Micah's prophesy was directed towards Judah, confronting God's people for their idolatry.
“The word of the Lord that came to Micah of Moresheth in the days of Jotham, Ahaz, and Hezekiah, kings of Judah, which he saw concerning Samaria and Jerusalem. Hear, all you peoples! Listen, O earth, and all that is in it! Let the Lord God be a witness against you, the Lord from His holy temple. For behold, the Lord is coming out of His place; He will come down and tread on the high places of the earth. The mountains will melt under Him, and the valleys will split like wax before the fire, like waters poured down a steep place. All this is for the transgression of Jacob and for the sins of the house of Israel. What is the transgression of Jacob? Is it not Samaria? And what are the high places of Judah? Are they not Jerusalem? Therefore I will make Samaria a heap of ruins in the field, places for planting a vineyard; I will pour down her stones into the valley, and I will uncover her foundations. All her carved images shall be beaten to pieces, and all her pay as a harlot shall be burned with the fire; All her idols I will lay desolate, for she gathered it from the pay of a harlot, and they shall return to the pay of a harlot. For it has come to Judah; it has come to the gate of My people, To Jerusalem.” (Micah 1:1-9)
Jotham was mighty. He was also blessed because he prepared his ways before the Lord, keeping God first and not turning away from the Lord to idolatry. Much of what Jotham did was soon to be undone by his son, Ahaz, next in line to reign as king in Judah. (2 Kings 15:32-38; 2 Chronicles 27)