A census tract is a small subdivision of a county or similar governmental institution containing 1,200 to 8,000 residents that is created with the intent of studying population changes between census years. Census tract numbers consist of up to four digits followed up two decimal places and are used to identify all the physical addresses found within the census tract subdivision.
Census tracts are the smallest population measurements that are available on the national level. The boundaries of census tracts usually correspond to legal and political boundaries found in urban areas. Although the area of a tract may expand or contract depending on population growth or movement, the number designating the general position of the tract almost never changes. Instead, researchers affix decimal suffixes to illustrate such changes.
As of the 2010 Census, numbers in the 9400s designate Native American tribal locations, numbers in the 9800s designate special land use areas such as large parks, and numbers in the 9900s designate large bodies of water.
The federal government offers an address search tool to identify the census tract number that corresponds to a specific street address. However, the census website claims that the most effective and accurate way to determine the number is to compare the street map to a map of the census tract.