The First Courthouse was built on the current site in 1807 from the proceeds of the sales of lots in Mercer at a cost of $7,116. The courthouse was a square structure of brick, two stories high, with wings on the east and west sides of the first story. The lower story was occupied by the court room. The upper story was divided into jury rooms and the wings housed the county offices. In 1840 the wings were taken down and large additions were made at a cost of $1,500. The building was then destroyed by fire in 1866, but all official records were saved from the fire.

The Second Courthouse was built immediately after the first Courthouse burned down at a cost of $100,000. It was made of red brick with stone trimmings and was surmounted by a belfry to which was later added a town clock. This Courthouse then burned down in December 1907. All official records were saved from the fire.

The Present Courthouse was erected in 1909 at a cost of approximately $500,000. The contractor suffered a huge loss since he had bid it at $324,000. The architect was Charles F. Owsley.