This study explores the demand and supply oriented factors that may contribute to the size of nonprofit organizations in the U.S. communities. This research tests demand theory, which indicated that nonprofit organizations grow more in communities where large service demand exists and when there is a service gap between community demand and government service supply. On the other hand, supply theories contend that nonprofit organizations are prevalent where a community carries the supply of human capital and financial resources and these supply of human and economic capital will mobilize nonprofit organizations to fulfill civic duties. For the scientific test of demand and supply theories, this study employs hierarchical linear model (HLM) and develops a longitudinal data set from multiple sources such as Department of Housing and Urban Development and National Charitable Center for Statistics, and Census. The proposed model analyzes how demand and supply indicators explain homeless serving nonprofit organizations size. The size of homeless service nonprofit was measured by three indicators: number of nonprofits, revenue of nonprofits and number of shelter beds. The findings of HLM analyses confirmed some of demand and supply factors that contribute homeless service nonprofit size. The communities with higher level of chronic homeless population …