On January 13, 1846, the legislative body of the Indiana Territory authorized creation of twelve counties in the Iowa Territory, with general descriptions of their boundaries. This brought the number of counties in the Iowa Territory to 22.
By the end of 1846, the Iowa portion of the Indiana Territory had been accepted into the Union as the State of Iowa (December 28, 1846). By 1851, the new state had grown to the extent that the original 22 counties needed to be divided into smaller, more accessible units. Accordingly, on January 15, 1851, the Iowa General Assembly enacted an omnibus bill which created 43 new counties. by reducing the previous counties. Sac County was named after the Sauk people, at that time called Sac Indians.
It took some time for the new organization to fully function. Sac City was designated the county seat in 1856, and construction of the first county courthouse was complete in 1862. By 1873 the burgeoning population had outgrown that structure and a larger (85 x 56 feet brick) building was authorized to replace it.
The new courthouse, complete with impressive bell tower, was placed in service in January 1874, and was used until 1888 when it burned.
To replace that structure, the present courthouse was built. It was enlarged and remodeled in the 1980s.