The township started to experience major growth after World War I and World War II as part of a general trend of population movement from nearby cities to the suburbs. In the early 1920s, subdivision activity along inter-city trolley lines led to a building spurt in Palmer Township, which doubled the population within 10 years. As a result, the township became seen as a desirable place to live for people who worked in other areas of the Lehigh Valley. The population saw further growth in the late 1940s and early 1950s due to the expansion of water lines and the development of low-income housing.