The brick Lake County courthouse was built in 1871 and in 1970 became the first courthouse in California to be placed on the National Register of Historic Places. Since 1978, it has housed the county museum.
Extensive collections of stone tools found within the county are on display, including arrowheads and ax heads and a stone plow.
The museum's Native American Room features a diorama of a Pomo Village, with a scale model of a tulle hut.
There are also research materials including historic photographs dating to the middle of the nineteenth century. The Lake County Genealogical Society has more than 1000 volumes about pioneer families.