Mercer County is named for John F Mercer, who was an American lawyer, painter and politician from Virginia and Maryland.
Surrounding County Courthouses:
N – Decatur County, Iowa and Wayne County, Iowa
E – Putnam County and Sullivan County
S – Grundy County
W – Harrison County
Created: February 14, 1845 
County Seat:
Princeton 1845 – present
County Courthouse – Princeton
Location: 802 East Main Street / Broadway Street
Built: 1911 – 1913
Style: Classical Revival
Architect: R W Van Trump and Rae Sanneman of Kansas City
Contractor: J E Anderson of Kansas City.
Description: The building faces north and is a two story gray colored stone and concrete structure. The rectangular shaped building is located on landscaped grounds in the center of Unionville. The building is 65 feet by 90 feet. The north front has a projecting portico supported by four high columns with a pediment above at the roof line. There is stone trim around the main entrance. A projecting cornice runs below the flat roof line. In the interior, there is a 300 person assembly room on the first story. The large County Circuit Court courtroom is located on the second story. The building houses the County Circuit Court. of the 3rd Judicial Circuit.
See: The 3rd Judicial Circuit includes Grundy County, Harrison County, Mercer County and Putnam County.
History: The county was created in 1845 and Princeton was designated as the county seat. The first courthouse was a two story log structure built in 1847. The second courthouse was a brick structure built in 1858 by H B Nesbitt at a cost of $8,000. The third and present courthouse was constructed in 1911 to 1913 at a cost of $76,000.
County Courthouse – Princeton
Photos taken 2009