In the mid-590s BC he worked to promote renewed conflict against Cirrha over Salamis. In 594 BC he was made archon of Attica, in order to subdue the civil disorder that was rampant there. He introduced a set of ordinances, seisachtheia, that did much to improve conditions. His ordinances were such a success that he was given the task of rewriting the constitution, creating what was later called the Solonian Constitution, which incorporated the first elements of democracy in world history.
He repealed most of the laws of Draco and introduced a timokratia, an oligarchy with a sliding scale of rights determined by property and productive capacity, dividing the population into four classes:
- Pentakosiomedimnoi ("500-bushel men", i.e., those who produced 500 bushels of produce per year),
- Hippeis (knights, i.e., those who could equip themselves and one cavalry horse for war, valued at 300 bushels per year),
- Zeugitai (tillers, i.e., owners of at least one pair of beasts of burden, valued at 200 bushels per year) and
- Thetes (manual laborers);
N.G.L. Hammond supposes that he instituted a graduated tax upon these upper classes at a rate of 6:3:1, with the lowest class of thetes paying nothing in taxes but being ineligible for elected office.
He introduced the trial by jury; military obligations were codified based on class; the Council of the Four Hundred (or Boule) and the Areopagus were established as the main consultative and administrative bodies; he introduced many new laws, especially those covering debt and taxation; he remodelled the calendar; he created a court for the lowest classes called the Heliaia and allowed it to audit those passing from the office of archon for each year; and he regulated weights and measures. Also, he took measures to protect children from sexual abuse. His laws were written onto special wooden cylinders and placed in the Acropolis.
Solon wrote the laws as a compromise between oligarchy and democracy, tailored to what the people would accept.
After having his constitution accepted, Solon exacted the promise of the city that his constitution would not change unless he were to change it himself, and then he left Athens for over ten years, travelling to Egypt, Cyprus and Lydia. This way he assured his work would have a fair chance to show its worth.
During his trip to Egypt he visited the temple of Neith in the district of Sais. The priests of Neith gave him information on their old history records, which Solon wrote down in manuscript. It was this manuscript that Plato used in his dialogues Timaios and Critias.
He is also presented by historian Herodotus of Halicarnassus in his historical accounts as a comment on the human condition. When in Lydia, he offended Croesus when asked, "Who is the happiest man you have ever seen?" by answering, "I can speak of no one as happy until they are dead" instead of complimenting the king. It was recalling this story which, again according to Herodotus, saved Croesus from execution when his kingdom was overcome by Cyrus' invading Persians.