Established in 1803, Cadiz is the County Seat of Harrison County Ohio.  The town is named for Cadiz, Spain and was laid at the junction of roads coming from Pittsburgh, Pennsylvania and Washington, Pennsylvania.  By 1846, 4 churches and 21 stores made their home in a town of 1,028 residents.

Manufacturing goods and processing farm products were the main vocations of the time.

Cadiz played an important part in the Civil War as portal in the Underground Railroad. Coal mining, both surface and underground, became the main industry in the twentieth century.

Today, the Utica/Marcellus shale industry is finding its home in Cadiz and surrounding Harrison County with the construction of a cryogenic facility, which includes multiple plants and a de-ethanization facility.