  susquehanna township is a township in dauphin county, pennsylvania, united states. the population was 24,036 at the 2010 census. this represents a 9.8% increase from the 2000 census count of 21,895. susquehanna township has the postal zip codes 17109 and 17110, which maintain the harrisburg place name designation. the township is a suburb of harrisburg, pennsylvania and is connected to marysville by the rockville bridge, the world's longest stone-arch rail bridge at the time of its completion. ==history== susquehanna township is located adjacent to the city of harrisburg in dauphin county. the name susquehanna is probably derived from a tribe of indians known as the susquehannocks. prior to june 4, 1785, what is now dauphin county was part of lancaster county. after the legislature created dauphin county it was basically divided into three townships: upper paxtang, middle paxtang and lower paxtang. 
Populated_places_established_in_1815 Townships_in_Dauphin_County,_Pennsylvania