The town of Henrietta was originally established prior to the Civil War; however, due to Indian hostilities, the city ceased to exist when early settlers abandoned their homesteads for the safety areas farther east protected by military posts. In 1873, both the city and county were reorganized by the legislature and Henrietta was designated the county seat. According to legend, a group of citizens from the nearby town of Cambridge stole the courthouse records for a brief period and claimed Cambridge as the county seat. A group of "cowboys" from Henrietta roped the safe with records intact and dragged the "courthouse" back to Henrietta. It served as the only court of justice for a 300-mile area until 1879.
The Immigrant Trail, the famous wagon train route of westward bound pioneers in the late 1800s, crossed Clay County south of Henrietta. The trail has been mapped and stones indicate its crossings at highway locations.
Today, Henrietta serves as a retail center with its economy based on agriculture, farming, and light industry.
A red granite monument at the northwest corner of the courthouse square stands as a war memorial with names of veterans who lost their lives in WWI, WWII, Korea and Vietnam.