Harmarville was settled by farmers and by immigrant coal miners who worked in the Harmar Mine (now closed).
Because of the Allegheny River, the Pennsylvania Turnpike and other highways and railroads, Harmarville has a strong history as a transportation center. Early industries included brick manufacturing. Later, such endeavors as the Gulf Research Center and the Harmarville Rehabilitation Center were located here. Brick manufacturing is still active in nearby Indiana Township on Rich Hill Road.
Of historic interest are the company houses for the Harmar Mine, located at the lower end of Guy's Run Road and the Harmarville Presbyterian Church, built in 1804 on the Denny farm.