In Fall 2007 the Horace Hagedorn Foundation funded the Center for Urban Research to help the foundation improve its grantmaking work on immigration issues by providing Census-related information that would help to better understand the changes in Hispanic demographics throughout Long Island. At a time when national attention has focused on the strain between established residents and newly arrived immigrants in this suburban region, the Foundation supports creative community and public-private initiatives that work to diminish these tensions. Our maps and data analysis will provide valuable tools in support of this important work. This case study describes how we used Census data sets, geographic information system (GIS) software, and statistical analysis for one component of our work for the Foundation -- estimating the Hispanic population on Long Island at the level of state legislative districts (Senate and Assembly) and county legislative districts. We estimate total Hispanic population, foreign- and native-born Hispanic population, and the population of Hispanics eligible to vote (citizens 18 and over) by legislative district.