What is a Census Block?
A census block is an area bounded by visible features such as streets, roads, streams, and railroad tracks and nonvisible features such as the boundaries of governmental units and other legal entities. A block is the smallest geographic area for which the Census Bureau collects and tabulates statistical data. Census blocks may look like a city block or may be large and irregularly shaped, depending upon features. The boundary of a state or a county is always a block boundary. Census blocks are numbered within census tracts and are unique to the census tract to which they belong. Census block numbers contain a 4-digit number plus one alpha character, if applicable, e.g. 3001A. Suffixes, such as 2011A and 2011B, reflect boundary changes as well as added features.