Mariposa County is known as the Mother of California Counties. One of the original twenty-seven counties of the new state of California, admitted into the Union in September 1850, Mariposa then embraced one fifth the area of the state. Ten other counties have since been created in whole - or in part - from Mariposa's initial boundaries.

In 1852 the county seat was moved from Agua Fria, and the courthouse was built in 1854.

Materials for the wooden structure came from a pine forest within a mile of the courthouse site. There the timbers were cut, sawn into rough lumber at a nearby sawmill, and some of it hand planed into finished lumber. Corners were formed by mortise and tenon. Nails were hand made and square cut.

In 1866 a clock was imported from England and installed in a tower built for that purpose. The hourly tolling of the clock is heard daily throughout the Town of Mariposa.

The architectural style of the original courthouse is Greek Revival, the preferred style for public buildings during much of the 19th century. The tower, with its crenellated parapet, is more Gothic Revival in style.

When the courthouse was nominated for the National Register in 1977, it was already the oldest courthouse in active use as a courthouse west of the Mississippi.

Excerpted from the 1977 NRHP nomination form.

Mariposa County Courthouse is California Historical Landmark No. 670.