Harker Heights is located near Fort Cavazos, a major United States Army post that was designated a permanent military facility in 1950.

Cox, Sam Garth Jr., and Barney Sissom created GIASISCO Corporation, which was meant to help expand the town from 400 to 950 acres (160 to 380 ha).

The city limits extend south to hills overlooking Stillhouse Hollow Lake on the Lampasas River.

Highway 190 is a four-lane freeway that passes through the city, connecting Killeen to the west with Interstate 35 in Belton 12 miles (19 km) to the east, at a point about halfway between Waco and Austin.

The population is heavily engaged in economic activities directly or indirectly related to the U.S. Army at nearby Fort Cavazos.

The climate in this area is characterized by hot, humid summers and generally mild to cool winters.

[13] In 2022, city voters approved the decriminalization of possession of misdemeanor amounts of marijuana,[14] although it is still illegal under state law.