The Circuit Court was the highest judicial authority in Hancock County.

The circuit court system was established in 1814 in Illinois Territory. The courts were given civil and criminal jurisdiction, and were originally presided over by a member of the Supreme Court assigned to the circuit. With the admission of Illinois to the Union in 1824, five circuits were established with separate judges appointed to the circuit courts. Hancock County was formed in 1825, with the original courthouse in Montebello. In 1827 the circuit judges were removed and replaced by the Supreme Court justices. In 1833 the Hancock County courthouse was moved to Carthage. In 1835, separate circuit judges were again appointed and a sixth circuit created. This continued until 1841, when the circuit courts were again dissolved and the Supreme Court judges returned to the circuit courts. Then, with the Constitution of 1848, the courts again were placed under the direction of circuit judges.