After the East Tennessee, Virginia and Georgia Railroad was built, crossing the Holston River at the town site, the name Union was adopted.

As of the 2020 United States census, there were 1,822 people, 842 households, and 541 families residing in the city.

28.2% of all households were made up of individuals, and 11.0% had someone living alone who was 65 years of age or older.

The climate in this area has mild differences between highs and lows, and there is adequate rainfall year-round.

[12] On January 1, 2010, the department installed a speed camera on US Highway 11E that reportedly issued 1,662 tickets in its first six months.

[13] However the town's budget for FY 2017 reports expected "Speed Cameras" revenue of $600,000.

This represents the largest single income line item for the city at 35% of total operating revenue.