The Old Harrison County Courthouse, located in Magnolia, Iowa, United States, was built in 1873.

It was listed on the National Register of Historic Places in 1983 as a part of the County Courthouses in Iowa Thematic Resource.

The county raised the funds for its construction by selling town lots.

[4] The building was condemned as unsafe in 1873, and the county's third courthouse was built the same year.

The generally rectangular structure is faced with brick laid in a common bond.