The county was named for William D. Gage, a Methodist minister who served as the first chaplain of the Nebraska Territorial Legislature.

In the Nebraska license plate system, Gage County is represented by the prefix 3 (it was the county with the third-largest number of vehicles registered in the state when the license plate system was established in 1922).

The Big Blue River runs south-southeast through the central part of the county.

[8] As of the 2000 United States Census,[15] there were 22,993 people, 9,316 households, and 6,204 families in the county.

29.20% of all households were made up of individuals, and 15.00% had someone living alone who was 65 years of age or older.

Since then, it has become a Republican stronghold, aside from the 1964 election in which Democrat Lyndon B. Johnson won the county in the midst of his national landslide victory.