Holt County is a county located in the northwestern portion of the U.S. state of Missouri. As of the 2020 census, the population was 4,223. It's county seat is Oregon. The county was organized February 15, 1841. Originally named Nodaway County, it was soon renamed for David Rice Holt (1803–1840), a Missouri state legislator from Platte County.

Nodaway County is a county located in the northwest part of Missouri. As of the 2020 census, the population was 21,241. Its county seat is Maryville. The county was organized February 14, 1845, and is named for the Nodaway River. It is the largest in area of the counties added to Missouri in the 1836 Platte Purchase and the fourth-largest county by area in Missouri.