The county was formed in 1847 and named for the military officer John C. Fremont, and was organized in 1850 and Austin was its first county seat. Court was held in a storeroom. In 1851, the county seat moved to Sidney where, in 1860, a $40,000 courthouse was constructed. This was a two-story building with a heavy brick tower and a tin roof. In the winter of 1863, the windows and doors of the entire structure were blown out by someone using two kegs of stolen gunpowder. The county spent a lot of money on repairs, but the upper floor and roof were too badly damaged to be repaired.
The present courthouse, a brick building, was built in 1889. It is fairly simple, but the classic early American architectural style provides it with plenty of character. Between short granite columns at the front of the building are cement steps that have become concave with wear from thousands of footsteps over the years.