[4] The county was named for Charles Henry Morrill, a president of the Lincoln Land Company.

[5] The terrain of Morrill County consists of low rolling hills.

The rock was a prominent landmark on the Oregon Trail, and has become a symbol of Nebraska, appearing on the state's license plates and on its commemorative quarter.

[8][9][10] As of the 2000 United States Census,[18] 5,440 people, 2,138 households, and 1,494 families resided in the county.

[19] The Humane Society of the United States awarded Sheriff Johyn D. Edens the 2009 Humane Law Enforcement Award for his investigation of mistreatment of 200 mustangs on an animal sanctuary.

[20] The owner of the Three Strikes Ranch, Jason Meduna, was sentenced to two consecutive 20-60 month terms, by Judge Leo Dobrovolny at the Morrill County Courthouse.

[21][22] In the May 13, 2010, Republican primary, Milo Cardenas and Travis Petersen, polled 379 votes each (there being no Democratic candidate), and the decision was due to be made between then by a game of chance such as a coin flip, subject only to a recount.

"[24] Thus Cardenas went forward to the final ballot, scheduled for November 2010,[25] with no other registered candidates.

[27] As of 2017, the county was part of the state's 47th legislative district,[28] and was represented in the Nebraska Legislature by Steve Erdman; Erdman is a member of the Republican Party, though the legislature is officially nonpartisan.