The county forms the core of
the Nemaha Half-Breed Reservation formed in the Fourth Treaty of
Prairie du Chien in 1830 as land for the offspring of traders and Native
Americans. The grounds of modern Indian Cave State Park mark where
the county's first community -- St. Deroin, Nebraska was founded in
1853 by members of the reservation as a trading post on the Missouri River.
When white settlement was permitted in the Kansas-Nebraska Act of 1854
it was part of Forney County (named for U.S. cabinet member John W. Forney)
which stretched along the Little Nemaha River from the Missouri River to west
of Lincoln, Nebraska. In 1855 Nemaha County was formally founded with
Brownville as its county seat. Johnson County was initially part of Nemaha but
was subsequently spun off.
Brownville was the biggest city in Nebraska at
the time and several firsts occurred in the county including: in 1861 the first
state normal school which was founded at what today is Peru
State College and Daniel Freeman filing the first claim under
the Homestead Act for land on January 1, 1863 at the
Brownville land office.
The Nebraska State Fair was held in
the county at Brownville in 1870-1871.
In 1883 the county seat was moved to Auburn.