[2] The county was named for Thomas Jefferson, third President of the United States of America.

In the Nebraska license plate system, Jefferson County is represented by the prefix 33 (it had the thirty-third-largest number of vehicles registered in the county when the license plate system was established in 1922).

Jefferson County was founded on January 26, 1856, and its governing structure was organized in 1864.

[5] In 2010, the Keystone-Cushing Pipeline (Phase II) was constructed south out of Jefferson County.

The terrain of Jefferson County consists of low rolling hills, whose leveled tops are largely used for agriculture.

Jefferson County is strongly Republican, having only backed the Democratic Party presidential candidate five times since 1900.