The Harmon Museum, also sometimes referred to as the Lebanon Museum, is housed in historic Harmon Hall. Built in 1913 as a recreational facility by the real estate mogul and philanthropist William Elmer Harmon, Harmon Hall was donated to the City of Lebanon. 

Harmon was born and raised in Lebanon and complained there was no place to play when he was a child. He gave the city Harmon Hall, Harmon Park (he established more than 120 across the country), Harmon Golf Course, and endowed the Harmon Civic Trust to maintain the properties. Harmon Hall was state of the art for 1913, equipped with exercise machines (yes, those weird ones), a basketball court (you can still see part of the court in the General Store on the Village Green), and a two-lane bowling alley (now the Farm Heritage Gallery).

It became a YMCA in 1946 and served as such until it was leased to the Warren County Historical Society in 1961 for its museum. The society bought the hall in 1981 and built an addition. It is now an acclaimed county museum that holds more than 30 exhibits across three floors.